src/vs/workbench/api/common/extHostDiagnostics.ts/DiagnosticCollection/delete
class DiagnosticCollection:	delete(uri: vscode.Uri): void {
		this._checkDisposed();
		this._onDidChangeDiagnostics.fire([uri]);
		this._data.delete(uri);
		if (this._proxy) {
			this._proxy.$changeMany(this._owner, [[uri, undefined]]);
		}
	}