Drop support for EOL Python 3.8

[hugovk]

https://devguide.python.org/versions/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (052a36e) to head (6398cdf).
Report is 1 commits behind head on main.

@@            Coverage Diff             @@
##              main      #650    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           18        18            
  Lines         2149      2149            
  Branches       245        97   -148     
==========================================
  Hits          2149      2149            

Flag	Coverage Δ
Python_3.10.15	100.00% <100.00%> (ø)
Python_3.11.10	100.00% <100.00%> (ø)
Python_3.12.6	?
Python_3.12.7	100.00% <100.00%> (?)
Python_3.13.0	100.00% <100.00%> (?)
Python_3.13.0-rc.2	?
Python_3.8.18	?
Python_3.9.20	100.00% <100.00%> (ø)

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

Files with missing lines	Coverage Δ
bedevere/gh_issue.py	100.00% <100.00%> (ø)
bedevere/util.py	100.00% <100.00%> (ø)