DOC: update sphinx to latest version

[hucorz]

What do these changes do?

update doc dependency: sphinx>=8.0.0

Using Sphinx 4.5.0 will fail when building xorbits's doc

Related issue number

Fixes #xxxx

Check code requirements

• tests added / passed (if needed)
• Ensure all linting tests pass

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.10%. Comparing base (d6465c9) to head (d2c6538).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #104      +/-   ##
==========================================
- Coverage   88.97%   85.10%   -3.88%     
==========================================
  Files          48       54       +6     
  Lines        4038     4559     +521     
  Branches      770      834      +64     
==========================================
+ Hits         3593     3880     +287     
- Misses        358      584     +226     
- Partials       87       95       +8     

Flag	Coverage Δ
unittests	84.93% <ø> (-3.88%)	⬇️

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[luweizheng]

LGTM