Restore the flag "Show managed UI for managed users"

[belext]

This flag allowed to disable "Managed by your organization" notifications in Settings:

Removed back in Chromium 77: https://github.com/chromium/chromium/commit/81ccee3c1849f0f1b5fb6e30048cb8033c80d594

Group policies are quite useful. For example you can:

• Disable Google Cast completely https://github.com/win32ss/supermium/issues/640#issuecomment-2144595353
• Remove "Get image descriptions from Google" context menu item: AccessibilityImageLabelsEnabled (suddenly started being added for me, probably after I tried enabling "Live Caption" on YouTube)
• Disable feedback sending: UserFeedbackAllowed

Configured policies can also be viewed on the chrome://policy page.

[win32ss]

This would be good to add considering the increased usage of group policies in Supermium.