[iOS] Remove video ambiance decoration in new Playlist UI

[kylehickinson]

This feature was unfortunately causing multiple issues:

• The very act of adding a new AVPlayerItemVideoOutput to AVPlayerItem caused audio-stutters when disconnecting the player layer from the player for background audio
• It caused the AVPlayerLayer to break upon being restored back to the AVPlayer until paused + played
• It caused high CPU usage which likely contributed to user reports of their phones getting hot while using the new playlist.

For now this will be removed until we can find an alternative solution

Resolves brave/brave-browser#42468

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[brave-builds]

Released in v1.75.47

[Uni-verse]

Verified on iPhone 12 running iOS 18.0 using version 1.75 (48)

• Confirmed that audio pauses/stutters when locking screen / backgrounding using 1.75 (44). Upgraded to 1.75 (48) and ensured that there is no audio disruptions when locking/unlocking and backgrounding.
• Ensured that enabling Enable Background Audio does not change the how audio transitions when playing in background.
• Ensured there are no audio issues using playlist controls as well as moving to and from PiP.