fix(CI): Try to wait for the mysql container in case it did not start…

… yet

Attempt to fix this "random" mysql error we see on CI:
ERROR 2013 (HY000): Lost connection to MySQL server at 'reading initial communication packet', system error: 2

Signed-off-by: Joas Schilling <213943+nickvergessen@users.noreply.github.com>

.github/workflows/phpunit-mysql.yml

@@ -58,6 +58,7 @@ jobs:
 
       - name: Enable ONLY_FULL_GROUP_BY MySQL option
         run: |
+          sleep 5
           echo "SET GLOBAL sql_mode=(SELECT CONCAT(@@sql_mode,',ONLY_FULL_GROUP_BY'));" | mysql -h 127.0.0.1 -P 4444 -u root -prootpassword
           echo "SELECT @@sql_mode;" | mysql -h 127.0.0.1 -P 4444 -u root -prootpassword