Drop support for Python 3.6

[alessiamarcolini]

As Pandas recently dropped support for Python 3.6
pandas-dev/pandas#34472

[leriomaggio]

👍 for me. I don't see reasons why we shouldn't.

[lorenz-gorini]

Probably one of the main reasons of the original choice we did with Alessia was related to mlpy dependency inside dap/base.py in reference_interval repository.
I previously replaced the mlpy code in commit https://github.com/HK3-Lab-Team/reference_interval/commit/2bb5edc5197cf56584ec0f31874ef6fc1af8f5b5#diff-e808e08e43ff321cfbd3ccdef30c9c8a5f99d02faeb698f992c990bacb67c8f1 (and merged in PR https://github.com/HK3-Lab-Team/reference_interval/pull/6 ). So I do not see direct issues related to this. 🙏

[leriomaggio]

No worries. However, mlpy support has to be dropped - effective immediately - in all the projects we do have.
Too much of a burden to carry, for No real benefit.

This has to happen gradually, of course; but the sooner, the better.

[lorenz-gorini]

No worries to you too 😃. That was the only mlpy dependency we had in any project, and it is no longer present (https://github.com/HK3-Lab-Team/reference_interval/issues/1 )

[leriomaggio]

Thanks Zeus for that! 🤙 👏