Avoid external link in search swagger

api/client-server/search.yaml

@@ -88,8 +88,12 @@ paths:
                       filter:
                         type: object
                         title: Filter
+                        # Within the C-S spec document, `filter`_ is picked up
+                        # as a link to the filtering section. In OpenAPI 3.0,
+                        # we could use the link feature, but we're still on 2.0
+                        # for now :/
                         description: |-
-                          This takes a `filter <https://matrix.org/docs/spec/%CLIENT_RELEASE_LABEL%/client_server.html#filtering>`_.
+                          This takes a `filter`_.
                       order_by:
                         title: "Ordering"
                         type: string

specification/client_server_api.rst

@@ -880,6 +880,8 @@ Where $streamtoken is an opaque token which can be used in another query to
 get the next set of results. The "start" and "end" keys can only be omitted if
 the complete dataset is provided in "chunk".
 
+.. _`filter`:
+
 Filtering
 ---------