Fix typo in jsonschema-use-cases.xml

Author: justinyaodu

specs/jsonschema-use-cases.xml

@@ -148,7 +148,7 @@
             <section title="Semantic annotation" anchor="uc-annotations">
                 <t>
                     There is a need to annotate values within a JSON document: for machine readability, and for documentation purposes.
-                    Given a document and directions for annotating it, you should should be able to:
+                    Given a document and directions for annotating it, you should be able to:
                 </t>
                 <list>
                     <t>document the meaning of a property,</t>