GIT_SILENT Update Appstream for new release

(cherry picked from commit 882c5b65)

org.kde.cantor.appdata.xml

@@ -134,9 +134,9 @@
     <binary>cantor</binary>
   </provides>
   <releases>
+    <release version="21.04.1" date="2021-05-13"/>
     <release version="21.04.0" date="2021-04-22"/>
     <release version="20.12.3" date="2021-03-04"/>
     <release version="20.12.2" date="2021-02-04"/>
-    <release version="20.12.1" date="2021-01-07"/>
   </releases>
 </component>