minor #5713 Upgrade-Guide: fix typo (staabm)
minor #5713 Upgrade-Guide: fix typo (staabm)

This PR was submitted for the master branch but it was merged into the 3.0 branch instead.

Discussion
----------

Upgrade-Guide: fix typo

Commits
-------

55f212ff0 Upgrade-Guide: fix typo

FriendsOfPHP/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,keradus/PHP-CS-Fixer,FriendsOfPHP/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,keradus/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer