Add policy templates as a dep to policy-related browser tests

This will cause any change to the //components/policy:policy_templates
target to also trigger these browser_tests.

Earlier, a policy_template change landed that caused browser_test
failures: https://crrev.com/c/6806258. But since GN wasn't aware that
those policies can affect the results of browser_tests, no such tests
were run on the CQ for that change.

By adding them as a dep, that will trigger tests for any policy_template
change in the CQ, and prevent such CLs from mistakenly being submitted
by the CQ.

Bug: None
Change-Id: Ifb7045a578280780f532c4fea29f3a618237884b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6822439
Reviewed-by: Sébastien Lalancette <seblalancette@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Amarjot Gill <amarjotgill@chromium.org>
Reviewed-by: Yann Dago <ydago@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1499686}