Don't quote the default issue closing regex.

It turns out that regex escapes and YAML quoted-scalar escapes don't play
nicely together.

config/gitlab.yml.example

@@ -49,7 +49,7 @@ production: &base
     ## Automatic issue closing
     # If a commit message matches this regular express, all issues referenced from the matched text will be closed
     # if it's pushed to a project's default branch.
-    # issue_closing_pattern: "^([Cc]loses|[Ff]ixes) +#\d+"
+    # issue_closing_pattern: ^([Cc]loses|[Ff]ixes) +#\d+
 
     ## Default project features settings
     default_projects_features: