A version >= 0.9.4 required for py-black. Added latest, which is
0.10.0. Manually verified that the .tar.gz for v0.9.3 used to generate
the sha256 matched the previous md5.
- remove the old LGPL license headers from all files in Spack
- add SPDX headers to all files
- core and most packages are (Apache-2.0 OR MIT)
- a very small number of remaining packages are LGPL-2.1-only
