Bugfix FXIOS-10552 - Odd behavior when using Privacy Window in Stage Manager

[PARAIPAN9]

:scroll: Tickets

Jira ticket Github issue

:bulb: Description

• Remove old code that was handling the privacy view.
• Adapt Privacy Window for iPad multi window feature.

Video

:pencil: Checklist

You have to check all boxes before merging

• [x] Filled in the above information (tickets numbers and description of your work)
• [x] Updated the PR name to follow our PR naming guidelines
• [ ] Wrote unit tests and/or ensured the tests suite is passing
• [ ] When working on UI, I checked and implemented accessibility (minimum Dynamic Text and VoiceOver)
• [x] If needed, I updated documentation / comments for complex code and public methods
• [ ] If needed, added a backport comment (example @Mergifyio backport release/v120)

[mobiletest-ci-bot]

	Messages
:book:	Project coverage: 33.2%
:book:	Edited 2 files
:book:	Created 0 files

Client.app: Coverage: 31.31

File	Coverage
BrowserViewController.swift	4.76%	⚠️
PrivacyWindowHelper.swift	0.0%	⚠️

Generated by :no_entry_sign: Danger Swift against 426cec1b270d884c30b13ad6ca80e5e78a2d4e81

[PARAIPAN9]

Thanks @mattreaganmozilla for your useful comments!!