[2.7] docker_container: fix memory_swappiness documentation (#47378)

* Documentation for docker_container: fix documentation for memory_swappiness. Default value will not equal 0, it will be inherited from the host machine (#47296)


(cherry picked from commit 4c2efa4b67)

* Add changelog.

changelogs/fragments/47296-docker_container-memory_swappiness.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+- "docker_container - fix ``memory_swappiness`` documentation."

lib/ansible/modules/cloud/docker/docker_container.py

@@ -218,7 +218,7 @@ options:
   memory_swappiness:
     description:
         - Tune a container's memory swappiness behavior. Accepts an integer between 0 and 100.
-    default: 0
+        - If not set, the value will be remain the same if container exists and will be inherited from the host machine if it is (re-)created.
   name:
     description:
       - Assign a name to a new container or match an existing container.