Added/updated operationIds according to today's updates in the spec

Signed-off-by: Alexey Rusakov <ktirf@users.sf.net>

api/client-server/list_joined_rooms.yaml

@@ -32,6 +32,7 @@ paths:
       summary: Lists the user's current rooms.
       description: |-
         This API returns a list of the user's current rooms.
+      operationId: getJoinedRooms
       security:
         - accessToken: []
       responses:

api/client-server/rooms.yaml

@@ -237,7 +237,7 @@ paths:
       summary: Get the m.room.member events for the room.
       description:
         Get the list of members for this room.
-      operationId: getRoomMembers
+      operationId: getMembersByRoom
       parameters:
         - in: path
           type: string
@@ -307,6 +307,7 @@ paths:
       description:
         This API returns a map of MXIDs to member info objects for members of the room. The current user must be in the room for it to work, unless it is an Application Service in which case any of the AS's users must be in the room.
         This API is primarily for Application Services and should be faster to respond than ``/members`` as it can be implemented more efficiently on the server.
+      operationId: getJoinedMembersByRoom
       parameters:
         - in: path
           type: string