Remove calls to clear_cache from Git::Wiki
Remove calls to clear_cache from Git::Wiki

They were probably added to compensate for tests shortcomings, but now
they don't complain.

Closes gitaly#1095

mmkassem/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,dreampet/gitlab,iiet/iiet-git,iiet/iiet-git,axilleas/gitlabhq,jirutka/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,axilleas/gitlabhq,jirutka/gitlabhq,mmkassem/gitlabhq,jirutka/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,jirutka/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,iiet/iiet-git,iiet/iiet-git,mmkassem/gitlabhq,stoplightio/gitlabhq