Notifications: do not rely on admin-bar styles (#13690)

* Notifications: do not rely on admin-bar styles

Follow up from #13450

In some cases, admin-bar styles may be dequeued (like when the Masterbar module is active).

* Stop dequeuing style when we need it (when notes is active)

This also adds the dependency back:
#13690 (comment)

modules/masterbar/masterbar.php

@@ -209,7 +209,13 @@ public function admin_body_class( $admin_body_classes ) {
 	 * Remove the default Admin Bar CSS.
 	 */
 	public function remove_core_styles() {
-		wp_dequeue_style( 'admin-bar' );
+		/*
+		 * Notifications need the admin bar styles,
+		 * so let's not remove them when the module is active.
+		 */
+		if ( ! Jetpack::is_module_active( 'notes' ) ) {
+			wp_dequeue_style( 'admin-bar' );
+		}
 	}
 
 	/**