Revert "Remove unnecessary? import hack"

This reverts commit 39805bc.

Author: Dave Bartolomeo

extensions/ql-vscode/src/queryserver-client.ts

@@ -1,5 +1,7 @@
 import * as cp from 'child_process';
-import { DisposableObject } from 'semmle-vscode-utils';
+// Import from the specific module within `semmle-vscode-utils`, rather than via `index.ts`, because
+// we avoid taking an accidental runtime dependency on `vscode` this way.
+import { DisposableObject } from 'semmle-vscode-utils/out/disposable-object';
 import { Disposable } from 'vscode';
 import { CancellationToken, createMessageConnection, MessageConnection, RequestType } from 'vscode-jsonrpc';
 import * as cli from './cli';