do not commit api_c.rst (generated)

[jquast]

• Keep docs/api_c.rst current and fail tox -e docs when it is stale
• Generate docs/api_c.rst instead of committing it
• also "cleanup" after tox -e asan

[codspeed]

Merging this PR will not alter performance

✅ 121 untouched benchmarks

---

_{Comparing jq/c-api-auto-update (65d6693) with master (6fef337)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.49%. Comparing base (6fef337) to head (65d6693).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #274   +/-   ##
=======================================
  Coverage   87.49%   87.49%           
=======================================
  Files          41       41           
  Lines        5614     5614           
  Branches     1501     1501           
=======================================
  Hits         4912     4912           
  Misses        324      324           
  Partials      378      378           

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