It would be nice for editors to be able to see the particular edit
that was their 100th, 1000th, etc. This patch changes the link of the
edit count thanks notification to the diff of the edit, rather than the
page the edit was on.
Note that this link will only work for newly created notfications. Past
edit count notification database entries do not store what revision id
the edit was on in the 'echo_events' table, so there is no way to link
to them unless the table is updated.
Bug: T326998
Change-Id: If81fd71ce6f99ad3883a3bfbfbd798270f762d37
