Skip permission check when screen-sharing with SCContentSharingPicker

SCContentSharingPicker allows screen-sharing on MacOS without the
OS-level screen recording permission. Thus there is no longer a need to
check for that permission when screen-sharing, or present users with
access to the system settings to enable the permission.

Bug: 364318237
Change-Id: Ibc70d9e13aed72d0f570e45c73de17f40389cf2e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5850932
Reviewed-by: Elad Alon <eladalon@chromium.org>
Commit-Queue: Tove Petersson <tovep@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1353974}