Hide email in "New chat"-list for trusted contacts

[zeitschlag]

Subtitle-Label gets hidden if chat.isProtected.
I'm not super happy with hiding the subtitleLabel but it's one of two reasonable approaches:

1. Hide the subtitleLabel
2. Override the subtitle of the ViewModel to be nil

Another option would have been to cleanup and declutter the ViewModel-stuff but this wouldn't have been pragmatic or reasonable.

Closes #2272.

[r10s]

lgtm - and hiding the subtitle makes sense to me as well :)

for the condition, see below, that needs to be tweaked.