Rename initializing_rules_registry_unittest.cc

As follow-up to http://crrev.com/49693003, this CL renames initializing_rules_registry_unittest.cc to rules_registry_unittest.cc as the class InitializingRulesRegistry has been deleted.

BUG=312461

Review URL: https://codereview.chromium.org/71823002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235300 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235300