Use optional chaining for more method calls (#156938)

This rewrites code such as:

```ts
if (thing) {
    thing.method();
}
```

To the more concise:

```ts
thing?.method();
```

This was done using a simple find replace. I tried to keep the change pretty conservative so it only touches simple cases like above

src/vs/workbench/api/common/extHostComments.ts

@@ -620,9 +620,7 @@ export function createExtHostComments(mainContext: IMainContext, commands: ExtHo
 		$deleteCommentThread(threadHandle: number): void {
 			const thread = this._threads.get(threadHandle);
 
-			if (thread) {
-				thread.dispose();
-			}
+			thread?.dispose();
 
 			this._threads.delete(threadHandle);
 		}