Update .readthedocs.yaml to fix xlearn-cmake issue

[gramhagen]

Description

Fix read-the-docs build failures

Related Issues

Checklist:

• I have followed the contribution guidelines and code style for this project.
• [N/A] I have added tests covering my contributions.
• I have updated the documentation accordingly.
• This PR is being made to staging branch and not to main branch.

[codecov-commenter]

Codecov Report

Merging #1528 (ed6efe8) into staging (8c81724) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           staging    #1528   +/-   ##
========================================
  Coverage    62.12%   62.12%           
========================================
  Files           84       84           
  Lines         8397     8397           
========================================
  Hits          5217     5217           
  Misses        3180     3180           

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