[kcms/autostart] Add Exec line to KCM desktop file

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

BUG: 426737

kcms/autostart/package/metadata.desktop

@@ -142,6 +142,7 @@ Comment[zh_TW]=自動啟動應用程式
 Encoding=UTF-8
 Type=Service
 Icon=system-run
+Exec=kcmshell5 autostart
 X-KDE-Library=kcm_autostart
 X-KDE-ServiceTypes=KCModule
 X-KDE-FormFactors=desktop