[TG Sync] Remove isEligibleForSyncing check

This check was added as a rollout safety option in
crrev.com/c/5877310 but was never used. Basically, it wants to
exclude groups that are more than X days old not to be added to
sync the first time sync feature is launched. However, tab group
sync feature is already launched and there is no need for it.

Bug: None
Change-Id: Ie0cf855d26df21f8048899c118412f5bdbc21e63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6310755
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1425943}