irc/kvirc: fix plist - remove help/en/doc_rfc2812.html

Upstream removed data/doctemplates/rfc2812.template:
https://github.com/kvirc/KVIrc/issues/2640
This file used for generate:
%%DOCS%%share/kvirc/%%VER%%/help/en/doc_rfc2812.html

Reported by: pkg-fallout