Correct link syntax in zones.md (#7069)

Author: loic-sharma

src/content/libraries/async/zones.md

@@ -30,9 +30,9 @@ Review the techniques covered in
 [Futures and Error Handling](/libraries/async/futures-error-handling)
 before reading this article.
 
-[dart:async]: ({{site.dart-api}}/dart-async/dart-async-library.html)
-[`runZoned()`]: ({{site.dart-api}}/dart-async/runZoned.html)
-[`runZonedGuarded()`]: ({{site.dart-api}}/dart-async/runZonedGuarded.html)
+[dart:async]: {{site.dart-api}}/dart-async/dart-async-library.html
+[`runZoned()`]: {{site.dart-api}}/dart-async/runZoned.html
+[`runZonedGuarded()`]: {{site.dart-api}}/dart-async/runZonedGuarded.html
 
 Zones make the following tasks possible: