WP-432 Available fields for custom template tag not displaying for all s...

...hortcodes

Available listing attribute text is not displaying for all shortcode template types that allow either 'custom' or 'if' template tags.  This change removes the switch statement that was restricting the display.

Similar logic can be seen here: https://github.com/Placester/builder/commit/55710a39f456ebbe3758323d82d76d5f4ada2d0c