[Tab Group Parity] Remove the setting param for TabGroupCreationDialog

Remove the setting param from code logic, the physical setting as well
as the flag param for showing the TabGroupCreationDialog.

OBSOLETE_HISTOGRAM[TabGroups.ShowTabGroupCreationDialogSwitch.ToggledToState]=Removed feature

Bug: 378954972
Change-Id: Ic3d182ff37913a38874917e9d884b6f7e4aa5fd1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6019876
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Brandon Fong <bjfong@google.com>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1385886}