Tidy example inventories in "Developing Dynamic Inventory Sources" (#18758)

Thanks @adamchainz!

docs/docsite/rst/dev_guide/developing_inventory.rst

@@ -76,11 +76,14 @@ The data to be added to the top level JSON dictionary looks like this::
 
         "_meta": {
             "hostvars": {
-              "moocow.example.com"     : { "asdf" : 1234 },
+                "moocow.example.com": {
-              "llama.example.com"      : { "asdf" : 5678 }
+                    "asdf" : 1234
+                },
+                "llama.example.com": {
+                    "asdf": 5678
+                }
             }
         }
-
     }
 
 .. seealso::