Add Exec line to KCM desktop file

This got lost in the QML port and is needed for KRunner to find/open the KCM

CCBUG: 426737

src/kcm/package/metadata.desktop

@@ -69,6 +69,7 @@ Comment[zh_TW]=管理藍牙裝置
 Encoding=UTF-8
 Type=Service
 Icon=preferences-system-bluetooth
+Exec=kcmshell5 bluetooth
 X-KDE-ServiceTypes=KCModule
 X-KDE-Library=kcm_bluetooth
 X-KDE-PluginInfo-Author=Nicolas Fella