Clean-up extensions feature flags from tests - Part 3

This is part of removing the feature flags related to the released
extensions parental controls on Desktop:
`EnableExtensionsPermissionsForSupervisedUsersOnDesktop`
`kEnableSupervisedUserSkipParentApprovalToInstallExtensions`.

As the number of the affected
sources is too big, the changes will be done per test suite or per directory.

Bug: 321240770
Change-Id: I09624c5793a77ea8d033da1a96f33bbb3f1fc845
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6487990
Commit-Queue: Anthi Orfanou <anthie@google.com>
Reviewed-by: Liza Bipin <mlbipin@google.com>
Cr-Commit-Position: refs/heads/main@{#1451809}