Return a types.MarkdownString instace to extensions (#107415)

Fixes #107414

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

@@ -338,7 +338,9 @@ export namespace MarkdownString {
 	}
 
 	export function to(value: htmlContent.IMarkdownString): vscode.MarkdownString {
-		return new htmlContent.MarkdownString(value.value, { isTrusted: value.isTrusted, supportThemeIcons: value.supportThemeIcons });
+		const result = new types.MarkdownString(value.value, value.supportThemeIcons);
+		result.isTrusted = value.isTrusted;
+		return result;
 	}
 
 	export function fromStrict(value: string | types.MarkdownString): undefined | string | htmlContent.IMarkdownString {