Update Python support to reflect coming 3.7 EOL

This is similar in purpose to this PR merged into the pending
`case-utils` release:

References:
* casework/CASE-Utilities-Python#99

Signed-off-by: Alex Nelson <[email protected]>

Author: ajnelson-nist

setup.cfg

@@ -23,7 +23,7 @@ install_requires =
     prov
     pydot
 packages = find:
-python_requires = >=3.7
+python_requires = >=3.8
 
 [options.entry_points]
 console_scripts =