Change setup.py to allow pydicom>=3

[timcogan]

With minor changes to test_anon.py, all tests are passing with pydicom>=3.

[finetjul]

Thanks !

Some linting tests are failing though.
Did you check it still works with pydicom<3 ?

[timcogan]

No problem! The code should still work with pydicom<3.

[pchoisel]

Thank you for your contribution, the modifications look good and the test pass.
However, I'm not a fan of the Makefile, could you remove it ?
After that, I'll merge the modications

[pchoisel]

Thank you !