Fix #3020: Update UserAgent to iOS 14.3 version.

[iccub]

Summary of Changes

This pull request fixes #3020

Submitter Checklist:

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

Test Plan:

Compare user agent to Safari.

Test note: when testing on iOS simulator i noticed that Version/ part of UA can be 14.0.1. sometimes instead of .2,
both numbers should be fine.

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).