correct short license text to SPDX standard Apache-2.0

ala Chia-Network/chia-blockchain#19027

Author: altendky

setup.py

@@ -36,7 +36,7 @@ def read(fname):
     author="Mariano Sorgente",
     author_email="[email protected]",
     description=("A reference pool for the Chia blockchain."),
-    license="Apache",
+    license="Apache-2.0",
     packages=setuptools.find_packages(),
     install_requires=dependencies,
     extras_require=dict(