mail/rspamd: Update to 3.0

• Pet portclippy
• Reformat Makefile with portfmt

Changelog: https://rspamd.com/announce/2021/08/19/rspamd-3.0.html
PR: 257944
Approved by: maintainer timeout (> 1 month), ygy (mentor)
Differential Revision: https://reviews.freebsd.org/D32232