make `/titlebar show encwarn` available for muc

## Expected Behavior
when `/titlebar show encwarn` is used, `[unencrypted]` should always displayed on the titlebar when the chat is unencrypted by omemo, OX or OTR, no matter the chat is 1to1 or muc

## Current Behavior
only 1to1 chat display this warning

## Context
It is misleading to new user

## Environment
Profanity, version 0.13.1dev.makepkg.9bce23e0
