Dropping Python 3.7

[vzhurba01]

We're considering dropping support for Python 3.7 for the next release.
Per NEP 29, Python 3.7 drop schedule was almost a year ago and many associated libraries have already dropped it.

Let us know if there's concerns in having Python 3.7 dropped next release. Thanks!

[vzhurba01]

Release v12.1.0 drops Python 3.7 support for both Wheels and Conda. Closing.