add missing intent action for notifications settings (#462)

Co-authored-by: Hee Tatt Ooi <hee.tatt.ooi@sap.com>
Co-authored-by: Jakob Möller <jakob.moeller@sap.com>
Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/ExternalActionHelper.kt

@@ -120,6 +120,7 @@ object ExternalActionHelper {
                     context.packageName
                 )
             } else {
+                intent.action = "android.settings.APP_NOTIFICATION_SETTINGS"
                 intent.putExtra(
                     "app_package",
                     context.packageName