Load `/capabilities` endpoint on workers

Related to:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2656
- e4a25d022c

roles/custom/matrix-synapse/vars/main.yml

@@ -167,6 +167,7 @@ matrix_synapse_workers_generic_worker_endpoints:
   - ^/_matrix/client/(api/v1|r0|v3|unstable)/search$
   - ^/_matrix/client/(r0|v3|unstable)/user/.*/filter(/|$)
   - ^/_matrix/client/(api/v1|r0|v3|unstable)/directory/room/.*$
+  - ^/_matrix/client/(r0|v3|unstable)/capabilities$
 
   # Encryption requests
   # Note that ^/_matrix/client/(r0|v3|unstable)/keys/upload/ requires `worker_main_http_uri`