Fix #1697: Update empty wallet copy and styling

[kylehickinson]

Summary of Changes

This pull request fixes issue #1697

Submitter Checklist:

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

Test Plan:

• Enable rewards and create a wallet
• Assuming 0 balance, go to settings > wallet view details > verify copy is correct

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).