add correct classifier for licence

Author: Ogban Ugot

setup.py

@@ -22,7 +22,7 @@
     author_email="ogbanugot@gmail.com",
     license="MIT",
     classifiers=[
-        "License :: OSI Approved :: GNU License",
+        "License :: OSI Approved :: GNU General Public License v3 (GPLv3)"
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",
     ],