drive-menu: Fix launch-nautilus label

The user-visible name of nautilus is "Files", not "File" ...

https://bugzilla.gnome.org/show_bug.cgi?id=781235

extensions/drive-menu/extension.js

@@ -146,7 +146,7 @@ const DriveMenu = new Lang.Class({
 	this._monitor.get_mounts().forEach(Lang.bind(this, this._addMount));
 
 	this.menu.addMenuItem(new PopupMenu.PopupSeparatorMenuItem());
-	this.menu.addAction(_("Open File"), function(event) {
+	this.menu.addAction(_("Open Files"), function(event) {
 	    let appSystem = Shell.AppSystem.get_default();
 	    let app = appSystem.lookup_app('org.gnome.Nautilus.desktop');
 	    app.activate_full(-1, event.get_time());