Always allow the support.google.com for supervised users

This avoids some sites which are linked to from Chrome settings from
being blocked for supervised users with "only allow approved sites"
configured by their parent.

Bug: 1289267
Change-Id: I227e9b41261058ce0c93cc506b990535617d81e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3560406
Reviewed-by: Monica Basta <msalama@chromium.org>
Auto-Submit: James Lee <ljjlee@google.com>
Reviewed-by: Aga Wronska <agawronska@chromium.org>
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Cr-Commit-Position: refs/heads/main@{#987611}