enable calling tabgroups.update on a group that's saved

Bug: 323982812
Change-Id: I5a0cae410ad65f5892a5d25064da03f8396e5acc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5378422


Auto-Submit: David Pennington <dpenning@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1279060}