fix: invalid attribute in placement group (#258)

The actions client attribute name is `actions`

Author: jooola

hcloud/placement_groups/client.py

@@ -158,7 +158,7 @@ def create(
 
         action = None
         if response.get("action") is not None:
-            action = BoundAction(self._client.action, response["action"])
+            action = BoundAction(self._client.actions, response["action"])
 
         result = CreatePlacementGroupResponse(
             placement_group=BoundPlacementGroup(self, response["placement_group"]),