Close advanced search window in collectionViewItemTree notify() test

The test opened an advanced search window but never closed it, which
likely caused the intermittent failures in the ZoteroPane focus() test
"should shift-tab across the zotero pane".

test/tests/collectionViewItemTreeTest.js

@@ -2818,6 +2818,9 @@ describe("CollectionViewItemTree", function () {
 				assert.isTrue(notifySpy.calledOnce);
 				await notifySpy.returnValues[0];
 				notifySpy.restore();
+
+				searchWin.close();
+				await item.eraseTx();
 			});
 		});
 	});