[MM-67157] Remove format parameter requirement from client license endpoint (#37167)

* MM-67157: Remove unused format flag from /license/client endpoint

The `format` query parameter on the `/license/client` (and local
variant) endpoint was effectively dead: it was required but only ever
accepted the single value `old`, returning an error otherwise. This
mirrors the earlier removal of the same flag from `/config/client`,
where the server now ignores the parameter while clients continue to
send `format=old` for compatibility with pre-v11 servers.

The server no longer inspects the `format` parameter, so requests with
no format, `format=old`, or any other value all succeed. The unused
i18n string and the parameter/response documentation in the OpenAPI
spec are removed accordingly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Audz4JLNQN5SJxcPwyQBd

* MM-67157: document format=old retention in webapp client

Mirror the getClientConfig comment so the format=old query param on
getClientLicenseOld is not mistakenly removed; clients keep sending it
for compatibility with pre-v11 servers even though current servers now
ignore it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Audz4JLNQN5SJxcPwyQBd

* MM-67157: stop sending format=old from webapp client

Now that the server ignores the format parameter on /license/client,
drop format=old from the @mattermost/client getClientLicenseOld call and
update the e2e intercepts/helpers that matched the old query string.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Audz4JLNQN5SJxcPwyQBd

* Drop unneeded wildcard from license/client cy.intercept path

The format query param is gone from GET /license/client requests, so
the trailing * used to match it is no longer needed.

---------

Co-authored-by: Claude <noreply@anthropic.com>

api/v4/source/system.yaml

@@ -1013,20 +1013,9 @@
 
         No permission required but having the `manage_system` permission returns more information.
       operationId: GetClientLicense
-      parameters:
-        - name: format
-          in: query
-          required: true
-          description: Must be `old`, other formats not implemented yet
-          schema:
-            type: string
       responses:
         "200":
           description: License retrieval successful
-        "400":
-          $ref: "#/components/responses/BadRequest"
-        "501":
-          $ref: "#/components/responses/NotImplemented"
   /api/v4/license/load_metric:
     get:
       tags: