mediawiki: Update maintainers

David had asked to be replaced earlier in the year and recently, Christian stepped up, performing the most recent update and volunteering to be a maintainer.

Thanks to David for originally kicking off this project!

See <https://phabricator.wikimedia.org/T330367> for related discussion.

library/mediawiki

@@ -1,6 +1,6 @@
-Maintainers: David Barratt <[email protected]> (@davidbarratt),
-             Kunal Mehta <[email protected]> (@legoktm),
-             addshore <[email protected]> (@addshore)
+Maintainers: Kunal Mehta <[email protected]> (@legoktm),
+             addshore <[email protected]> (@addshore),
+             Christian Heusel <[email protected]> (@christian-heusel)
 GitRepo: https://github.com/wikimedia/mediawiki-docker.git
 GitFetch: refs/heads/main
 GitCommit: fdf347f62615dad789d0e703fc2f6d628c43d4e1