Remove Uphold custom header

[ShivanKaul]

We currently send Uphold a custom header x-brave-partner: uphold as specified in https://github.com/brave/brave-browser/wiki/Custom-Headers. Uphold should be able to work without this custom header, so we should remove it.

@pes10k

Test Plan:

Base test

1. Go to uphold.com
2. Verify that no custom header sent (i.e. x-brave-partner: uphold)

New Uphold account

(thanks @Miyayes)

1. Remove custom header for Uphold
2. Brave Browser > Brave Rewards > Verify wallet
3. Inside that flow, when prompted to log in/sign up for Uphold, create an account (given you don’t already have one). Note: this will require ID verification. Check if you’re ever taken out of the flow, or the account creation process loses context of the fact that you’re coming through Brave and trying to verify your Brave Rewards wallet
4. When you’re done, see if your Brave Rewards wallet is verified
5. Once verified, press “Withdraw funds” and press “Add funds” buttons on brave://rewards page
6. Disconnect from Uphold, and then link again (just have to log in again)

Existing Uphold account

Check if an existing Uphold account still works correctly.

[LaurenWags]

Verified passed with

Brave | 1.31.82 Chromium: 95.0.4638.40 (Official Build) beta (x86_64)
-- | --
Revision | e3e7c76ba0284b16087cf4cf3153abfaef6470c7-refs/branch-heads/4638@{#624}
OS | macOS Version 10.15.7 (Build 19H1417)

x-brave-partner: uphold - PASSED

Confirmed that the x-brave-partner: uphold is not sent with 1.31.x.

1.30.x	1.31.x

Clean Profile - link existing KYC account - PASSED

Confirmed that existing Uphold account could be linked to a clean profile. Confirmed that balance displayed as expected and I could perform a tip without issue.

Example	Example

Upgrade Profile - KYC account linked prior to upgrade - PASSED

Also did an upgrade scenario. Had Uphold linked with 1.30.x and upgraded to 1.31.x. Confirmed still linked after upgrade and could view balance, etc. See #14602 (comment) for additional testing/notes.

Confirmed unable to connect non-KYC'd account - PASSED

1. Clean profile 1.31.x (staging env)
2. Enable Rewards, claim grant (balance is now 30 BAT)
3. Click Verify Wallet --> Select Uphold
4. Get taken to authorize. Authorize.
5. Choose sign up (minimum sign up - email, password, country, etc)
6. Get kicked back to brave://rewards telling me I need to complete verification w/ below message.

---

Verified PASSED using

Brave	1.31.81 Chromium: 95.0.4638.40 (Official Build) beta (64-bit)
Revision	e3e7c76ba0284b16087cf4cf3153abfaef6470c7-refs/branch-heads/4638@{#624}
OS	Linux

x-brave-partner: uphold - PASSED

Confirmed that the x-brave-partner: uphold header is not sent with 1.31.x.

1.30.x	1.31.x

Clean Profile - link existing KYC account - PASSED

Confirmed that existing Uphold account could be linked to a clean profile. Confirmed that balance displayed as expected and I could perform a tip without issue.

Example	Example

Upgrade Profile - KYC account linked prior to upgrade - PASSED

Also did an upgrade scenario. Had Uphold linked with 1.30.x and upgraded to 1.31.x. Confirmed still linked after upgrade and could view balance, etc.

Confirmed unable to connect non-KYC'd account - PASSED

1. Clean profile 1.31.x (staging env)
2. Enable Rewards
3. Click Verify Wallet --> Select Uphold
4. Get taken to authorize. Authorize.
5. Choose sign up (minimum sign up - email, password, country, etc)
6. Get kicked back to brave://rewards telling me I need to complete verification w/ below message.

---

Verification passed on

Brave | 1.31.82 Chromium: 95.0.4638.40 (Official Build) beta (64-bit)
-- | --
Revision | e3e7c76ba0284b16087cf4cf3153abfaef6470c7-refs/branch-heads/4638@{#624}
OS | Windows 10 Version 21H1 (Build 19043.1266)

x-brave-partner: uphold - PASSED

Confirmed that the x-brave-partner: uphold is not sent with 1.31.x.

1.30.x	1.31.x

Clean Profile - link existing KYC account - PASSED

Confirmed that existing Uphold account could be linked to a clean profile. Confirmed that balance displayed as expected and I could perform a tip without issue.

Example	Example

Upgrade Profile - KYC account linked prior to upgrade - PASSED

Also did an upgrade scenario. Had Uphold linked with 1.30.x and upgraded to 1.31.x. Confirmed still linked after upgrade and could view balance, etc.

Confirmed unable to connect non-KYC'd account - PASSED

1. Clean profile 1.31.x (staging env)
2. Enable Rewards, claim grant (balance is now 30 BAT)
3. Click Verify Wallet --> Select Uphold
4. Get taken to authorize. Authorize.
5. Choose sign up (minimum sign up - email, password, country, etc)
6. Get kicked back to brave://rewards telling me I need to complete verification w/ below message.

[srirambv]

Verification passed on Oppo Reno 5 with Android 11 running 1.31.86 x64 build

x-brave-partner Header - PASSED

• Verified x-brave-parnter: uphold header is not sent

1.30.89	1.31.86

Clean Profile - link existing KYC account - PASSED

• Verified able to link an existing Uphold account to wallet on a clean install.
• Verified balance is displayed correctly
• Verified able to perform a tip without any issues

Upgrade Profile - KYC account linked prior to upgrade - PASSED

• Verified linking Uphold on 1.30.89 and upgraded to 1.31.86 retained Uphold wallet connection and balance was shown correctly