push_to_pull_request: Fix handling of .git.

This was throwing the "you can't access the repo" error for this
reason.

tools/push-to-pull-request

@@ -29,8 +29,8 @@ remote_url="$(git config remote."$remote".url)"
 repo_fq="$(echo "$remote_url" | perl -lne 'print $1 if (
     m, ^ git\@github\.com:
          ([^/]+ / [^/]+)
-         (?:\.git)?
-       $ ,x )')"
+         (\.git)?
+       $ ,x )' | sed 's/.git$//')"
 
 if [ -z "$repo_fq" ]; then
     # We're pretty specific about what we expect the URL to look like;