GIT_SILENT Update Appstream for new release

(cherry picked from commit 3fd62327)

src/org.kde.k3b.appdata.xml

@@ -259,9 +259,9 @@
     <binary>k3b</binary>
   </provides>
   <releases>
+    <release version="20.08.3" date="2020-11-05"/>
     <release version="20.08.2" date="2020-10-08"/>
     <release version="20.08.1" date="2020-09-03"/>
     <release version="20.08.0" date="2020-08-13"/>
-    <release version="20.04.3" date="2020-07-09"/>
   </releases>
 </component>