Helm Chart: Ensure mariadb port value can be set (#4844)

* Helm Chart: Ensure mariadb port value can be set
- fixes #4843

* Allow for missing mariadb.port
Without this we get the opposite error
```
Error: values don't meet the specifications of the schema(s) in the following chart(s):
console:
- mariadb.port: Invalid type. Expected: integer, given: null
```
have now tested with and without mariadb.port and now in both cases we get the expected `DB_PORT` value in the rendered template

deploy/kubernetes/console/values.schema.json

@@ -300,7 +300,7 @@
           }
         },
         "port": {
-          "type": "null"
+          "type": ["integer", "null"]
         },
         "resources": {
           "type": "object",