Remove support for Python 3.8

[codecov[bot]]

Codecov Report

Merging #157 (fdc9107) into master (94297cb) will increase coverage by 0.20%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #157      +/-   ##
==========================================
+ Coverage   93.23%   93.43%   +0.20%     
==========================================
  Files          45       44       -1     
  Lines        1226     1218       -8     
==========================================
- Hits         1143     1138       -5     
+ Misses         83       80       -3     

Impacted Files	Coverage Δ
src/tickit/core/management/event_router.py	97.80% <100.00%> (ø)