Jelly: Remove Jelly flag from add SMB share dialog

Jelly has launched and this conditional code can be cleaned up.

Bug: b:319740292
Test: Manually verify dynamic colors supported in dialog
Change-Id: I55dd9b1bd8b85118f969c91dc618b6d442142133
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5421244


Commit-Queue: Wes Okuhara <wesokuhara@google.com>
Reviewed-by: Wenbo Jie <wenbojie@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1282204}