Updates for AmberTools 24

[mattwthompson]

Packages aren't up yet: conda-forge/ambertools-feedstock#141

There doesn't appear to be a new GAFF bundled compared to 23 (#281)

$ head -n1 amber24_src/dat/leap/parm/gaff*dat                                                              14:38:42
==> amber24_src/dat/leap/parm/gaff.dat <==
AMBER General Force Field for organic molecules (Version 1.81, May 2017)

==> amber24_src/dat/leap/parm/gaff2.dat <==
AMBER General Force Field for organic molecules (Version 2.2.20, March 2021)

==> amber24_src/dat/leap/parm/gaff211.dat <==
AMBER General Force Field for organic molecules (Version 2.11, May 2016)

Haven't looked at what other change(s) are relevant here