Use cases: add a missing word

Author: awwright

jsonschema-use-cases.xml

@@ -116,7 +116,7 @@
 
             <section title="Domain-specific language">
                 <t>
-                    Application authors may use an entirely self-contained inside an application that consumes JSON. By using a declarative language, the application requirements can be better optimized by the application.
+                    Application authors may use an entirely self-contained schema inside an application that consumes JSON. By using a declarative language, the application requirements can be better optimized by the application.
                 </t>
                 <t>
                     Application authors may define custom hooks and processing for the JSON (without need for standardizing the customization).