remove work-around for twine bug

[KrisThielemans]

As pypa/twine#1216 is now fixed, remove our workaround.

With any luck, it fixes the problem in conda-forge/petsird-feedstock#1 that the license file isn't packaged.

[KrisThielemans]

https://github.com/ETSInitiative/PETSIRD/actions/runs/14397309167/job/40375262163#step:10:190

adding license file 'LICENSE'

but https://github.com/ETSInitiative/PETSIRD/actions/runs/14397309167/job/40375262163#step:10:303

Checking dist/petsird-0.3.1.dev9+g00e33b0-py3-none-any.whl: ERROR    InvalidDistribution: Invalid distribution metadata: unrecognized or    
         malformed field 'license-file'; unrecognized or malformed field        
         'license-expression'       

So, still hitting pypa/twine#1216. Checking pypa/twine#1217, it added the following

       if version.Version(meta.get("metadata_version", "0")) < version.Version("2.4"):
             meta.pop("license_files", None)
             # Support for metadata version 2.4 requires packaging version 24.1
             # or later. When parsing metadata with an older packaging, the
             # invalid License-File fields are not understood and added to the
             # unparsed dictionary. Remove them to avoid triggering the
             # following check.
             unparsed.pop("license-file", None)

@casperdcl are we still missing something? Or does our toolchain need to be updated?