Fix documentation to match schema

Including "binddata" and "version" in a Site Script caused it to fail.
Changing the schema reference at the top allowed VSCode to highlight the error, indicating that those aren't allowed.
Removing them resolved the issue.

Seems the schema is being 'more-enforced' in SPO now more than in the past.

Author: sparkitect

docs/declarative-customization/get-started-create-site-design.md

@@ -24,7 +24,7 @@ Each action is specified by the "verb" value in the JSON script. Also, actions c
    ```powershell
     $site_script = '
     {
-        "$schema": "schema.json",
+        "$schema": "https://developer.microsoft.com/json-schemas/sp/site-design-script-actions.schema.json",
             "actions": [
                 {
                     "verb": "createSPList",
@@ -64,9 +64,7 @@ Each action is specified by the "verb" value in the JSON script. Also, actions c
                         }
                     ]
                 }
-            ],
-                "bindata": { },
-        "version": 1
+            ]
     }
     '
    ```