pidgin/purple-plugin-pack

Remove plugin_pack.spec.in as we haven't provided rpms in a long time

Testing Done:
Ran `ninja dist` and verified no issues.

Reviewed at https://reviews.imfreedom.org/r/2404/
# IRC More
dependencies: libpurple
authors: Sadrul Habib Chowdhury,John Bailey
introduced: 2.2.0
notes: Support for /notice only when built with libpurple older than 2.4.0.
Adds additional IRC features, including a customizable quit message, a customizable CTCP VERSION reply, a rudimentary channel autojoin list and the /notice command for notices where libpurple does not support it.