appdata: update release info for 5.5.2

GIT_SILENT

Author: kossebau

org.kde.kdevelop.appdata.xml

@@ -141,6 +141,7 @@
     <category>IDE</category>
   </categories>
   <releases>
+    <release version="5.5.2" date="2020-06-02"/>
     <release version="5.5.1" date="2020-05-05"/>
     <release version="5.5.0" date="2020-02-02"/>
     <release version="5.4.6" date="2020-01-06"/>