Remove accidentally added UUID re-definition in storage schema

* docs/schemas/storageencryption.rng: Remove UUID definition
  since its provided by the domain.rng/storagevol.rng schemas
  that import this

docs/schemas/storageencryption.rng

@@ -29,15 +29,4 @@
     </element>
   </define>
 
-  <define name="UUID">
-    <choice>
-      <data type="string">
-        <param name="pattern">[a-fA-F0-9]{32}</param>
-      </data>
-      <data type="string">
-        <param name="pattern">[a-fA-F0-9]{8}\-([a-fA-F0-9]{4}\-){3}[a-fA-F0-9]{12}</param>
-      </data>
-    </choice>
-  </define>
-
 </grammar>