Fix #1696: Make "My First Ad" use a shorter dismissal duration

[kylehickinson]

Also ignores the debug override

Summary of Changes

This pull request fixes issue #1696

Submitter Checklist:

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

Test Plan:

• Enable rewards
• Install fresh build
• Go through onboarding, at my first ad, verify it disappears in 3s instead of 8s
• Verify a regular ad stays up for 8s (or whatever amount is set in the debug menu)

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).

[srirambv]

@kylehickinson is this still valid for actual ad? With #1773 ad time is increased to 30 sec