docs: enable RTD builds

[dboddie]

• Have you followed the guidelines for contributing?
• Have you signed the CLA?
• Have you successfully run make lint?
• Have you successfully run pytest tests/unit?

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[codecov-commenter]

Codecov Report

Merging #4258 (6e85bad) into main (36cc6f7) will decrease coverage by 0.03%.
The diff coverage is n/a.

❗ Current head 6e85bad differs from pull request most recent head df290b1. Consider uploading reports for the commit df290b1 to get more accurate results

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@@            Coverage Diff             @@
##             main    #4258      +/-   ##
==========================================
- Coverage   88.96%   88.94%   -0.03%     
==========================================
  Files         295      295              
  Lines       20151    20118      -33     
==========================================
- Hits        17928    17893      -35     
- Misses       2223     2225       +2     

see 18 files with indirect coverage changes

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