Only test and require Python 3.7+

https://github.com/pythonprofilers/memory_profiler/actions/runs/3627706309/jobs/6126859301

GitHub has dropped Python 3.5 and 3.6 support from the `setup-python` action.

Author: altendky

setup.cfg

@@ -23,7 +23,7 @@ classifiers =
 py_modules =
     memory_profiler
     mprof
-python_requires = >=3.5
+python_requires = >=3.7
 install_requires = psutil
 
 [options.entry_points]