Fix Issue #29- "[Core][Getting started dialog]: The Need help link on Getting started dialog is broken."

Fix Issue #29- "[Core][Getting started dialog]: The Need help link on Getting started dialog is broken."

Replace deprecated "clickable-link" class with simple href.

See also [pull request #157](https://github.com/adobe/brackets-edge-web-fonts/pull/157) in the Edge Web Fonts Extension repo.