refactor(templates): Drop support for Python 3.8 in templates

[edgarrmondragon]

Python 3.8 will reach EOL in about one month, so arguably there's no need for new plugins to support it.

• https://devguide.python.org/versions/
• https://endoflife.date/python

---

📚 Documentation preview 📚: https://meltano-sdk--2661.org.readthedocs.build/en/2661/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.20%. Comparing base (3d3ac7b) to head (60a550b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2661      +/-   ##
==========================================
- Coverage   90.24%   90.20%   -0.05%     
==========================================
  Files          58       58              
  Lines        4891     4891              
  Branches      963      963              
==========================================
- Hits         4414     4412       -2     
- Misses        329      331       +2     
  Partials      148      148              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[codspeed-hq]

CodSpeed Performance Report

Merging #2661 will not alter performance

_{Comparing edgarrmondragon/feat/drop-py38-templates (e46b319) with main (e997deb)}

Summary

✅ 6 untouched benchmarks