Fix #14957 - Virtuality is not selected when editing generated column

- added VIRTUAL STORED option for mariadb
Fixes: #14957

Signed-off-by: William Desportes <williamdes@wdes.fr>

templates/columns_definitions/table_fields_definitions.twig

@@ -98,6 +98,7 @@
     {% set options = {'': '', 'VIRTUAL': 'VIRTUAL'} %}
     {% if server_type == 'MariaDB' %}
         {% set options = options|merge({'PERSISTENT': 'PERSISTENT'}) %}
+        {% set options = options|merge({'STORED': 'STORED'}) %}
     {% else %}
         {% set options = options|merge({'STORED': 'STORED'}) %}
     {% endif %}