Fix 'Learn More' link within the picker for caller-info provider

Avoid constructing the Spanned object on the client-side as it
isn't Parcelable. Send the html-encoded text as the subtext instead,
which will be spanned within Discovery service wherein the dialog
originates.

Issue-Id: OPO-705
Change-Id: Icce7583364474ff75c747d38cdc5d1b2000ceac1
(cherry picked from commit 7f62e060)