Merge pull request #10333 from jlhawn/image_json_schema_reword

Updated image spec docs to clarify image JSON

image/spec/v1.md

@@ -114,7 +114,7 @@ This specification uses the following terms:
     </dd>
 </dl>
 
-## Image JSON Schema
+## Image JSON Description
 
 Here is an example image JSON file: