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/
nullclient = executable('nullclient', 'nullclient.c', 'defines.h',
c_args : ['-DSTANDALONE'],
dependencies : [libpurple_dep, glib])