BHV-14477: Add "enyo-unselectable" class to sample.

### Issue
Text in the `moon.DataGridListSample` can be highlighted/selected, and this is particularly noticeable when tapping the paging controls, as their icons are now implemented via a font.

### Fix
We add the `enyo-unselectable` class to the sample.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>