Run licence and optional dependency checks with 3.10

[jklaise]

Use Python 3.10 (previously 3.8) to run:

• licence checks
• optional dependency checks
  setup.cfg has been cleaned up to reflect that we're not checking licences on other versions of Python

[codecov]

Codecov Report

Merging #876 (b825513) into master (3343b95) will decrease coverage by 0.04%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #876      +/-   ##
==========================================
- Coverage   85.33%   85.29%   -0.04%     
==========================================
  Files          74       74              
  Lines        8768     8768              
==========================================
- Hits         7482     7479       -3     
- Misses       1286     1289       +3     

Flag	Coverage Δ
macos-latest-3.10	85.25% <ø> (+0.09%)	⬆️
ubuntu-latest-3.10	85.16% <ø> (-0.10%)	⬇️
ubuntu-latest-3.7	85.16% <ø> (-0.04%)	⬇️
ubuntu-latest-3.8	85.18% <ø> (ø)
ubuntu-latest-3.9	85.09% <ø> (-0.10%)	⬇️
windows-latest-3.9	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
alibi/datasets/default.py	93.47% <0.00%> (-2.18%)	⬇️