CI: use artifact to save sdist

[Zeroto521]

To fix CI can't upload sdist, see https://github.com/Zeroto521/my-data-toolkit/runs/3958875284?check_suite_focus=true#step:3:7

[codecov]

Codecov Report

Merging #242 (7c7e8cd) into master (15ad186) will decrease coverage by 0.97%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #242      +/-   ##
==========================================
- Coverage   99.80%   98.82%   -0.98%     
==========================================
  Files          21       21              
  Lines         512      512              
  Branches       51       51              
==========================================
- Hits          511      506       -5     
- Misses          0        3       +3     
- Partials        1        3       +2     

Impacted Files	Coverage Δ
dtoolkit/accessor/_util.py	80.00% <0.00%> (-20.00%)	⬇️
dtoolkit/accessor/dataframe.py	97.14% <0.00%> (-1.43%)	⬇️

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