[TabStrip] Hide NTB when tab strip is empty

Hide NTB when tab strip is empty.

Bug: 1413658
Change-Id: I07779e24438e152a471ad03311a075016d75cf0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4236905


Commit-Queue: Sirisha Kavuluru <skavuluru@google.com>
Reviewed-by: Sirisha Kavuluru <skavuluru@google.com>
Cr-Commit-Position: refs/heads/main@{#1118914}