Clean up usage of enable_notifications_refresh

The flag was enabled by default a long time ago.

Bug: 255877880
Test: ash_components_unittest
Change-Id: If34994b02d394c340587f828e51db8ae457d9e88
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5604609


Reviewed-by: Satoshi Niwa <niwa@chromium.org>
Commit-Queue: Yuichiro Hanada <yhanada@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312653}