Change MYSQL_PASSWORD to 'example'

mediawiki/stack.yml

@@ -22,5 +22,5 @@ services:
       # @see https://phabricator.wikimedia.org/source/mediawiki/browse/master/includes/DefaultSettings.php
       MYSQL_DATABASE: 'my_wiki'
       MYSQL_USER: 'wikiuser'
-      MYSQL_PASSWORD: ''
+      MYSQL_PASSWORD: 'example'
       MYSQL_RANDOM_ROOT_PASSWORD: 'yes'