minor symfony#10191 Update bugs.rst (Gun5m0k3)

This PR was submitted for the 4.1 branch but it was merged into the 2.8 branch instead (closes symfony#10191).

Discussion
----------

Update bugs.rst

The symfony2 tag redirects to the symfony tag, so link to it directly

<!--

If your pull request fixes a BUG, use the oldest maintained branch that contains
the bug (see https://symfony.com/roadmap for the list of maintained branches).

If your pull request documents a NEW FEATURE, use the same Symfony branch where
the feature was introduced (and `master` for features of unreleased versions).

-->

Commits
-------

22e432a Update bugs.rst

Author: xabbuh

contributing/code/bugs.rst

@@ -44,7 +44,7 @@ If your problem definitely looks like a bug, report it using the official bug
 
 * *(optional)* Attach a :doc:`patch <patches>`.
 
-.. _`Stack Overflow`: https://stackoverflow.com/questions/tagged/symfony2
+.. _`Stack Overflow`: https://stackoverflow.com/questions/tagged/symfony
 .. _IRC channel: https://symfony.com/irc
 .. _the Symfony Slack: https://symfony.com/slack-invite
 .. _tracker: https://github.com/symfony/symfony/issues