Remove deprecated function (#27605)

* make /ancillary a post

* remove get from client, fix tests

* remove GET for retrieving ancillary permissions

* Update permissions.yaml

* Update permissions.yaml

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

api/v4/source/permissions.yaml

@@ -1,35 +1,4 @@
   /api/v4/permissions/ancillary:
-    get:
-      tags:
-        - permissions
-      summary: Return all system console subsection ancillary permissions
-      description: >
-        Returns all the ancillary permissions for the corresponding system console
-        subsection permissions appended to the requested permission subsections.
-
-
-        __Minimum server version__: 5.35
-      operationId: GetAncillaryPermissions
-      parameters:
-        - name: subsection_permissions
-          in: query
-          description: >
-            The subsection permissions to return the ancillary permissions for.
-            These values are comma seperated.
-            Ex. subsection_permissions=sysconsole_read_reporting_site_statistics,sysconsole_write_reporting_site_statistics,sysconsole_write_user_management_channels
-          schema:
-            type: string
-      responses:
-        "200":
-          description: Successfully returned all ancillary and requested permissions
-          content:
-            application/json:
-              schema:
-                type: array
-                items:
-                  type: string
-        "400":
-          $ref: '#/components/responses/BadRequest'
     post:
       tags:
         - permissions