[BUG] rspamd manpage out-of-sync with rspamd --help

[comburent]

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Read about bug reporting in general: https://rspamd.com/doc/faq.html#how-to-report-bugs-found-in-rspamd
  • Enabled relevant debugging logs: https://rspamd.com/doc/faq.html#how-to-debug-some-module-in-rspamd
  • Checked the FAQs about Core files in case of fatal crash: https://rspamd.com/doc/faq.html#how-to-figure-out-why-rspamd-process-crashed
  • Tried ASAN package and obtained the ASAN report (if possible): https://rspamd.com/doc/faq.html#asan-builds
  • Checked that your issue isn't already filed: https://github.com/issues?utf8=%E2%9C%93&q=is%3Aissue+user%3Arspamd
  • Checked that there is not already an experimental package or master branch

Describe the bug
rspamd --help lists options that are not present in the rspamd manpage.

Steps to Reproduce

1. Run rspamd --help.
2. Run man rspamd.
3. Compare outputs. Observe that some options (e.g. --var) are not documented in the manpage.

Expected behavior
Manpage documentation is synchronized with rspamd --help.

Versions

$ rspamd --version
Rspamd daemon version 3.6

CPU architecture x86_64; features: avx2, avx, sse2, sse3, ssse3, sse4.1, sse4.2, rdrand
Hyperscan enabled: FALSE
Jemalloc enabled: FALSE
LuaJIT enabled: TRUE (LuaJIT version: LuaJIT 2.1.0-beta3)
ASAN enabled: FALSE
BLAS enabled: FALSE
Fasttext enabled: FALSE