[SharedTabGroups] Only present ungroup option for owners

Only the owner of a shared tab group will have the ungroup option in
the TabGroupEditorBubbleView.

This means members will only be able to hide and leave the shared group.

Non-shared group functionality is preserved.

No test is added since this is extremely hard to test.

Ideally, we would have a test where we share a group from one profile to another in order to verify which options show up in the editor bubble.

Additionally, we don't have a way to inject arbitrary data into the
DataSharingService or CollaborationService at the moment so even if we set up the test framework we will still be missing some pieces.

Change-Id: I7588cc9595ef960270b0c435c0282ba4f47cc0cd
Bug: 382754499
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6075432
Commit-Queue: Darryl James <dljames@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Reviewed-by: David Pennington <dpenning@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1393798}