Fix review deletion to properly clean up VS Code comments

Added await to getReviewThreads() call in deleteReview() method to ensure
comment threads are properly updated before the method returns. This allows
the review thread change event to fire and trigger cleanup of VS Code comment
threads associated with the deleted review.

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/github/pullRequestModel.ts

@@ -639,7 +639,7 @@ export class PullRequestModel extends IssueModel<PullRequest> implements IPullRe
 		this.hasPendingReview = false;
 		await this.updateDraftModeContext();
 
-		this.getReviewThreads();
+		await this.getReviewThreads();
 		this._onDidChange.fire({ timeline: true });
 		return {
 			deletedReviewId: databaseId,