pidgin/pidgin

Remove unused conversation-timestamp signal.

2020-10-29, Elliott Sales de Andrade
2b0b603bd39a
Remove unused conversation-timestamp signal.

It is registered, but never emitted.

Testing Done:
Built docs.

Reviewed at https://reviews.imfreedom.org/r/180/
subdir('libpurple')
subdir('protocols')
if ENABLE_GTK
subdir('pidgin')
endif
if enable_consoleui
subdir('finch')
endif