GIT_SILENT Update Appstream for new release

(cherry picked from commit 0ae4c294)

org.kde.kolourpaint.appdata.xml

@@ -383,9 +383,9 @@
     <binary>kolourpaint</binary>
   </provides>
   <releases>
+    <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"/>
-    <release version="20.12.0" date="2020-12-10"/>
   </releases>
 </component>