Bug 1635046 - Be consistent in ignoring .mozconfig / mozconfig files between git and hg. r=froydnj

Both were ignoring .mozconfig and mozconfig, but .hgignore was ignoring
mozconfig-foo and .mozconfig-foo, while git was not ignoring
mozconfig-foo.

Differential Revision: https://phabricator.services.mozilla.com/D73605

.gitignore

@@ -26,7 +26,7 @@ ID
 
 # User files that may appear at the root
 /.mozconfig*
-/mozconfig
+/mozconfig*
 /configure
 /old-configure
 /config.cache