small fixes to coverage, type hints, documentation, and QoL for Makefile

[jakkdl]

Description of Change

Minor issues I noticed while writing #1085. Split out from it to make the diff smaller.

Nothing in the checklist should be relevant for this, all the changes should be uncontroversial improvements.

Assumptions

Replace this text with any assumptions made (if any)

Checklist for All Submissions

• I have added change info to CHANGES.rst
• If this is resolving an issue (needed so future developers can determine if change is still necessary and under what conditions) (can be provided via link to issue with these details):
  • Detailed description of issue
  • Alternative methods considered (if any)
  • How issue is being resolved
  • How issue can be reproduced
• If this is providing a new feature (can be provided via link to issue with these details):
  • Detailed description of new feature
  • Why needed
  • Alternatives methods considered (if any)

Checklist when updating botocore and/or aiohttp versions

• I have read and followed CONTRIBUTING.rst
• I have updated test_patches.py where/if appropriate (also check if no changes necessary)
• I have ensured that the awscli/boto3 versions match the updated botocore version

[jakkdl]

codecov fail is a rate limit error:

debug - 2024-03-20 11:02:14,016 -- Commit creating result --- {"result": "RequestResult(error=RequestError(code='HTTP Error 429', params={}, description='{"detail":"Tokenless has reached GitHub rate limit. Please upload using a token: https://docs.codecov.com/docs/adding-the-codecov-token. Expected available in 827 seconds."}'), warnings=[], status_code=429, text='{"detail":"Tokenless has reached GitHub rate limit. Please upload using a token: https://docs.codecov.com/docs/adding-the-codecov-token. Expected available in 827 seconds."}')"}
error - 2024-03-20 11:02:14,016 -- Commit creating failed: {"detail":"Tokenless has reached GitHub rate limit. Please upload using a token: https://docs.codecov.com/docs/adding-the-codecov-token. Expected available in 827 seconds."}

[jakkdl]

same rate limit error as in #1101 (comment)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.30%. Comparing base (e8a3b8e) to head (d70635f).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1101   +/-   ##
=======================================
  Coverage   86.29%   86.30%           
=======================================
  Files          62       62           
  Lines        5889     5891    +2     
=======================================
+ Hits         5082     5084    +2     
  Misses        807      807           

Flag	Coverage Δ
unittests	86.30% <100.00%> (+<0.01%)	⬆️

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