[Tab Collection] Emit didRemoveTabGroup on tab close

Closing the last tab in a group did not correctly emit the
didRemoveTabGroup event. Update this to match TabGroupModelFilterImpl

While most listeners were tolerant to this, the StripLayoutHelper
thought the tab group remained hidden and subsequently subtracted a tab
group when rebuilding leading to a crash.

Fixed: 437085870
Change-Id: Ia2b6c83ac23d31037248181a02bdafe508d49984
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6895618
Commit-Queue: Fiaz Muhammad <mfiaz@google.com>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Auto-Submit: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Fiaz Muhammad <mfiaz@google.com>
Cr-Commit-Position: refs/heads/main@{#1507747}