[QS] Don't convert secondaryLabel to string

Both the InternetTileViewModel and QSTile were converting the (possibly
HTML) content description into a string, resulting in both displaying
the markup text as well as _not_ rendering the resulting Spanned string.

Fixes: 311254816
Test: manual using demo mode
Test: adb shell am broadcast -a com.android.systemui.demo -e command network -e mobile show -e level 3 -e datatype 5ge
Test: all sysui tests
Flag: NONE
Change-Id: I8d5c802a9c5253070c985763bdfc92017e1b3a99