Remove redundant show() / hide() in expand() / collapse()

PR microsoft#176641 cleaned up the redundant, explicit calls to these methods in
`toggleExpand()` as they already happen in the
`onDidChangeCollapsibleState` listener if `_expanded` doesn't match the
new collapsible state. `hide()` was also adjusted there to call
`deleteCommentThread()` as needed.

src/vs/workbench/contrib/comments/browser/commentThreadZoneWidget.ts

@@ -257,22 +257,12 @@ export class ReviewZoneWidget extends ZoneWidget implements ICommentThreadWidget
 		this.commentService.disposeCommentThread(this.owner, this._commentThread.threadId);
 	}
 
-	public collapse(): Promise<void> {
+	public collapse() {
 		this._commentThread.collapsibleState = languages.CommentThreadCollapsibleState.Collapsed;
-		if (this._commentThread.comments && this._commentThread.comments.length === 0) {
-			this.deleteCommentThread();
-			return Promise.resolve();
-		}
-
-		this.hide();
-		return Promise.resolve();
 	}
 
-	public expand(): Promise<void> {
+	public expand() {
 		this._commentThread.collapsibleState = languages.CommentThreadCollapsibleState.Expanded;
-
-		this.show(this.arrowPosition(this._commentThread.range), 2);
-		return Promise.resolve();
 	}
 
 	public getGlyphPosition(): number {