drop python 3.8 support

[MarcelWilson]

• Mypy version needs to be unlocked
• black version needs to be unlocked.
• possible code updates that we limited due to 3.8 (annotations, etc?)

[MarcelWilson]

Looks like we can also resolve the mypy overrides in silently.py -- python/mypy#2427
This should be done as well.