reference swarm page correctly

Signed-off-by: Batuhan Taşkaya <btaskaya33@gmail.com>

docs/user_guides/swarm_services.md

@@ -6,7 +6,7 @@
 
 Starting with Engine version 1.12 (API 1.24), it is possible to manage services
 using the Docker Engine API. Note that the engine needs to be part of a
-[Swarm cluster](../swarm.rst) before you can use the service-related methods.
+[Swarm cluster](../swarm.html) before you can use the service-related methods.
 
 ## Creating a service
 
@@ -66,4 +66,4 @@ Either the service name or service ID can be used as argument.
 
 ```python
 client.remove_service('my_service_name')
-```
\ No newline at end of file
+```