Use mw-ui for "All notifications" link

* Link is a cta to another step of the "show notification" process

* Be consistent with "Read as wiki page" in talk overlay
(I1c8c708056fcaa87d800b9726f4891293ef03e7c)

Change-Id: I6f20b6d9f7ecb8e2b3fbf282826d0c6046c8680f
Merge "Use mw-ui for "All notifications" link"