Fix #2402: Update copy for Auto-Contribute settings to match desktop

[kylehickinson]

Summary of Changes

This pull request fixes #2402

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()

Test Plan:

• Verify copy is changed

Screenshots:

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • release-notes/(include|exclude)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue is assigned to a milestone (should happen at merge time).

[iccub]

Leaving the milestone checkbox for you Kyle, unsure if we put it into 1.15.1

[kylehickinson]

Yeah I think this will go with 1.16