Fix markdown table of contents name for strings like # ff

Fixes #34644

extensions/markdown/src/tableOfContentsProvider.ts

@@ -79,7 +79,7 @@ export class TableOfContentsProvider {
 	}
 
 	private static getHeaderText(header: string): string {
-		return header.replace(/^\s*#+\s*(.*?)\s*\1*$/, (_, word) => `${word.trim()}`);
+		return header.replace(/^\s*#+\s*(.*?)\s*#*$/, (_, word) => word.trim());
 	}
 
 	public static slugify(header: string): string {