removed BSD license from metadata

I have no idea why the BSD license was in there, maybe a left over from the numkit
files that were in here before 0.7.0 ??? Anyway, it is highly confusing so make surew
that these meta data are not shown anymore on pypi and elsewhere.

pyproject.toml

@@ -18,7 +18,6 @@ classifiers = [
     "Environment :: Console",
     "Intended Audience :: Science/Research",
     "License :: OSI Approved :: GNU General Public License (GPL)",
-    "License :: OSI Approved :: BSD License",
     "Operating System :: POSIX",
     "Operating System :: MacOS :: MacOS X",
     "Operating System :: Microsoft :: Windows",