Fix: use email to get avatar URL

[glaubersilva]

Resolves GIVE-1165

Description

This PR change how we retrieve the donor avar URL in the Donor view, now instead of use the donor ID we are using the donor e-mail to make sure that the proper profile URL will be used.

As a note, the get_avatar_url() function, which is used under the hood, accepts the user e-mail or user id, so we were using it wrong before the changes implemented on this PR because the donor id is not the same one of the user id.

Affects

The donor's view.

Visuals

Testing Instructions

1. Create a test donation using a donor's email that has a Gravatar account set up.
2. Go to the donor's view page and make sure the proper avatar image (the same one from Gravatar) is displayed there.

Pre-review Checklist

• Acceptance criteria satisfied and marked in related issue
• Relevant @unreleased tags included in DocBlocks
• Includes unit tests
• Reviewed by the designer (if follows a design)
• Self Review of code and UX completed

[rickalday]

Passed QA tests.