Revert "mountpoint-util: tmpfs supports uid=/gid= mount options"

This reverts commit 7d4f00c88c.

fstype_can_uid_gid() is about fixating all files to the specified
uid/gid. tmpfs does not qualify. The uid/gid parameter there is simply
about the default uid/gid for the root inode of the tmpfs, it allows
setting uids/gid arbirarily for all inodes after that.

This distinction matters: for file systems this function returns true
for we can use this in place of uidmapped mounts. But for tmpfs this is
not going to work, given inodes on that fs can end up having arbitrary
uid/gid.

See: https://github.com/systemd/systemd/pull/25284#issue-1438427144

src/basic/mountpoint-util.c

@@ -480,7 +480,6 @@ bool fstype_can_uid_gid(const char *fstype) {
                           "iso9660",
                           "msdos",
                           "ntfs",
-                          "tmpfs",
                           "vfat");
 }