Display the system gallery storage permission as system fixed

Due to the WRITE_MEDIA_IMAGES app op, photos access cannot actually be
denied. Since the role is fixed, the permission effectively is, too

Bug: 315320090
Test: atest MediaPermissionTest#testGalleryAppListedAsFixed
Flag: EXEMPT see bug
Relnote: none
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:17f747d7ea2e2bb9ac5bbb7654bd5354eb4632d0)
Merged-In: If9ae5366fe80fcd9eaf9c45dcee13e163207fbbe
Change-Id: If9ae5366fe80fcd9eaf9c45dcee13e163207fbbe
1 file changed