fix: correct the copy-pasted docs for covar_pop and bool_or

[jackylee-ch]

Which issue does this PR close?

• N/A

Rationale for this change

The user_doc blocks for covar_pop and bool_or are verbatim copies of covar_samp and bool_and, so the SQL reference documents the wrong function. covar_pop is described as sample covariance, and bool_or as "true if all non-null input values are true" — the inverse of what it does.

Existing tests already show the behaviour differs: aggregate.slt gives covar_samp = 1 vs covar_pop = 0.666666666667 on the same data, and bool_and = false vs bool_or = true on the same column.

What changes are included in this PR?

Corrects the description, syntax_example and sql_example of both, and regenerates aggregate_functions.md.

What is the testing strategy for this PR?

Docs only; the behaviour is unchanged and already covered by the aggregate.slt cases cited above.

Are there any user-facing changes?

The SQL reference for covar_pop and bool_or is now correct. No API change.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.66%. Comparing base (5b389eb) to head (9dda3be).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24990      +/-   ##
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- Coverage   81.67%   81.66%   -0.01%     
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  Files        1126     1126              
  Lines      414524   414524              
  Branches   414524   414524              
==========================================
- Hits       338558   338541      -17     
- Misses      56054    56065      +11     
- Partials    19912    19918       +6     

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