Remove centralnotice-admin right assignments on 3 wikis

CentralNotice can only be changed from metawiki
(and testwiki for testing) so having the right on any
other wiki doesn't make any sense (and is confusing).

This configuration predates git blame so we can't find
out why it was added, but it's uncontroversial to remove.

Change-Id: I086920d00bd779441efc668300886181e2c328a1