biology/iqtree: Update to 2.4.0

Refer to the release notes for information about a bug that may impact
past results.

PR: 284746
Release Notes: https://github.com/iqtree/iqtree2/releases/tag/v2.4.0
Sponsored by: The FreeBSD Foundation

Co-authored-by: Alven <alster@vinterdalen.se>