Fix error in setup.py

PyPI doesn't recognize PyPy3 as a valid programming language

Author: tleonhardt

setup.py

@@ -57,7 +57,6 @@
 Programming Language :: Python :: 3.6
 Programming Language :: Python :: 3.7
 Programming Language :: Python :: Implementation :: CPython
-Programming Language :: Python :: Implementation :: PyPy3
 Topic :: Software Development :: Libraries :: Python Modules
 """.splitlines())))