Following the merging of #14959 - Gitea is a lot more strict regarding the interpretation of `X-Real-IP` and `X-Forwarded-For` headers.
This PR updates the fail2ban documentation to include hints to set: `REVERSE_PROXY_TRUSTED_PROXIES` and `REVERSE_PROXY_LIMIT` appropriately.
See discussion in #16443
Co-authored-by: zeripath <art27@cantab.net>