Revert to previous diff pruning behavior

Before 10.6.9, if a rugged diff met the conditions for being too-large (which obiously meant it was also collapsable), too-large would take precedence. This reverts the behavior back to that, since gitlab-ce depends on this

Closes #31 (closed)

Status changed to merged

Mentioned in commit 382275e1

@DouweM thanks for the review! Can we release 10.6.10? (and how do we make sure it appears on https://rubygems.org/gems/gitlab_git/versions ?)