update docstring of ibgp to reflect changes

gso/services/provisioning_proxy.py

@@ -62,8 +62,8 @@ def execute_playbook(
     .. code-block:: json
 
         "inventory": {
-            "_meta": {
-                "vars": {
+            "all": {
+                "hosts": {
                     "host1.local": {
                         "foo": "bar"
                     },
@@ -71,12 +71,6 @@ def execute_playbook(
                         "key": "value"
                     }
                 }
-            },
-            "all": {
-                "hosts": {
-                    "host1.local": null,
-                    "host2.local": null
-                }
             }
         }