move mw core code coverage

As a hack I have had the PHP Unit code coverage for MediaWiki core
generated at https://integration.wikimedia.org/coverage/  it is now
properly namespaces and uses a layout similiar to the doc.wm.o domain.

The new URL is now:

 https://integration.wikimedia.org/cover/mediawiki-core/master/php

bug: 31518
Change-Id: I7ab7f6188ac20a89d5dd858b1893bc993b742949