DOC use pull request builds of readthedocs for doc build check

[MatthewSZhang]

Checklist

• Used a personal fork to propose changes
• A reference to a related issue: DOC builds check issue of readthedocs #92
• A description of the changes: remove long-lived branches, e.g. 0.3.X and 0.4.X, for doc build check

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (84b2f83) to head (a301482).
⚠️ Report is 50 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #93   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          603       609    +6     
=========================================
+ Hits           603       609    +6     

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