GIT_SILENT Update Appstream for new release

(cherry picked from commit 415b70f6)

data/org.kde.kdenlive.appdata.xml

@@ -275,10 +275,10 @@
     </ul>
   </description>
   <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>
   <url type="homepage">https://kdenlive.org/</url>
   <url type="bugtracker">https://bugs.kde.org</url>