Remove patches for catching file browser selected items change

[jtpio]

Follow-up to #6888

#6888 added a few patches to be able to know when the file browser selected items change:

notebook/packages/tree-extension/src/index.ts

Lines 139 to 153 in fd45f31

	// TODO: use upstream signal when available to detect selection changes
	// https://github.com/jupyterlab/jupyterlab/issues/14598
	const selectionChanged = new Signal<FileBrowser, void>(browser);
	const methods = [
	'_selectItem',
	'_handleMultiSelect',
	'handleFileSelect',
	] as const;
	methods.forEach((method: (typeof methods)[number]) => {
	const original = browser['listing'][method];
	browser['listing'][method] = (...args: any[]) => {
	original.call(browser['listing'], ...args);
	selectionChanged.emit(void 0);
	};
	});

Ideally there should be a built-in signal emitted when this is the case. Tracked upstream in jupyterlab/jupyterlab#14598.

For this issue to be solved jupyterlab/jupyterlab#14598 would first have to be fixed and released in JupyterLab, so Notebook 7 can be updated with the latest versions of the packages.