client: Fix Chat Monitor missing sender brackets
Always re-add hidden sender brackets for the Chat Monitor as the
normal sender prefixes get replaced with Network, Buffer, and Sender
names.
Sender brackets shown:
> Copy-pasted
Chat Monitor: <Bitlbee:#channel> digitalcircuit does things
Channel: -*- digitalcircuit does things
Before:
> Copy-pasted with sender brackets hidden (wrong)
Chat Monitor: Bitlbee:#channel digitalcircuit does things
Channel: -*- digitalcircuit does things
After:
> Copy-pasted with sender brackets hidden (correct)
Chat Monitor: <Bitlbee:#channel> digitalcircuit does things
Channel: -*- digitalcircuit does things
Closes GH-314.