fix milestone link in github_stats

tools/github_stats.py

@@ -212,7 +212,7 b' if __name__ == "__main__":'
 
     print("We closed %d issues and merged %d pull requests." % (n_issues, n_pulls))
     if milestone:
-        print("The full list can be seen `on GitHub <https://github.com/%s/milestone/%s>`"
+        print("The full list can be seen `on GitHub <https://github.com/%s/milestones/%s>`_"
             % (project, milestone)
         )