Bump iqtree2 from 1320c4c to c401ac4

Bumps [iqtree2](https://github.com/iqtree/iqtree2) from `1320c4c` to `c401ac4`.
- [Release notes](https://github.com/iqtree/iqtree2/releases)
- [Commits](iqtree/iqtree2@1320c4c...c401ac4)

---
updated-dependencies:
- dependency-name: iqtree2
  dependency-version: c401ac489c9df73aa3f67c487e0384fe3c0cf436
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]