Prepare DiffRenderer to changed parameters for wikidiff2 1.8.0

Prepare DiffRenderer to changed parameters for wikidiff2 1.8.0

The config parameter handling in wikidiff2 will migrate completely to
phpini values. Due to that we will remove the php config variable
wgWikiDiff2MovedParagraphDetectionCutoff and its usage.

In the process of deleting the 4th parameter in the wikidiff2_do_diff()
method, this exception is added so deployment can be handled separately.

On the long run these exceptions will be removed completely and the
(then) current mediawiki will depend on wikdiff2 > 1.8.0

Bug: T194272
Depends-On: I673d2489d5bce1a24a6ea83e168704948564661b
Change-Id: I30262412b0784b84af88ffab6ed0694a08b671e9