Change EditShortcutsPreferenceFragment to use a Preference for subtitle/description

Replaces PreferenceCategory with unselectable Preference to better match desired visuals

Screenshot at https://x20web.corp.google.com/users/jo/jonesriley/dragToEdit/editScreenWithSubtitle.png

Flag: N/A
Test: N/A
Bug: 323388734
Change-Id: Ia1b333bc246ea4dd98070a646d5a8a1716ccbcee