Fix #1871: Change grant claimed copy for ads grants

[kylehickinson]

Needs translations pushed to transifex after

Summary of Changes

This pull request fixes issue #1871

Submitter Checklist:

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

Test Plan:

• At the moment, easiest way is to fake the grant type at GrantClaimedViewController creation.

Screenshots:

Regular Grant	Ads Grant

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]

Let me know when we should push to transifex, perhaps there's more string changes incoming

[kylehickinson]

There'll be more strings coming here: #443