remove dead code

appStoreId is never set to be cleared

src/apps.js

@@ -1274,8 +1274,6 @@ function update(app, data, auditSource, callback) {
     // this allows cloudron install -f --app <appid> for an app installed from the appStore
     if (app.manifest.id !== updateConfig.manifest.id) {
         if (!data.force) return callback(new BoxError(BoxError.BAD_FIELD, 'manifest id does not match. force to override'));
-        // clear appStoreId so that this app does not get updates anymore
-        updateConfig.appStoreId = '';
     }
 
     // suffix '0' if prerelease is missing for semver.lte to work as expected