Remove TabConnectednessDecorator

This component is not used anymore, and it has a non-zero runtime cost
that prevents running PerformanceManager on the main thread.

Bug: None
Change-Id: Icd6b7f5cff08a0176d98c99f3981fe0413f5f23b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5593028


Reviewed-by: Patrick Monette <pmonette@chromium.org>
Commit-Queue: Anthony Vallée-Dubois <anthonyvd@chromium.org>
Reviewed-by: Sun Yueru <yrsun@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1310108}