Fix Dataclass Doc about dataclass_json import problem

[Future-Outlier]

It should be from dataclasses_json import dataclass_json.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.94%. Comparing base (c512571) to head (dfb5c22).
Report is 114 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5533      +/-   ##
==========================================
+ Coverage   60.45%   60.94%   +0.48%     
==========================================
  Files         778      796      +18     
  Lines       50318    51640    +1322     
==========================================
+ Hits        30420    31471    +1051     
- Misses      17061    17264     +203     
- Partials     2837     2905      +68     

Flag	Coverage Δ
unittests-datacatalog	69.31% <ø> (ø)
unittests-flyteadmin	58.73% <ø> (+0.04%)	⬆️
unittests-flytecopilot	17.79% <ø> (ø)
unittests-flytectl	67.41% <ø> (ø)
unittests-flyteidl	79.04% <ø> (?)
unittests-flyteplugins	61.85% <ø> (ø)
unittests-flytepropeller	57.29% <ø> (ø)
unittests-flytestdlib	65.59% <ø> (ø)

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