chore: remove requirements.txt and setup.py

[jombooth]

As a follow-up to our Poetry migration, remove requirements.txt and setup.py, and all references to these files. Deps are determined by pyproject.toml and poetry.lock now.

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✅ Deploy Preview for heartex-docs canceled.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (dcfa931) 75.89% compared to head (1b9aec7) 75.89%.
Report is 6 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #5345   +/-   ##
========================================
  Coverage    75.89%   75.89%           
========================================
  Files          154      154           
  Lines        12926    12926           
========================================
  Hits          9810     9810           
  Misses        3116     3116           

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