[Docs] Align Code lines of StructuredDataset with Flytesnacks Example

[JiangJiaWei1103]

Why are the changes needed?

The code lines of StructuredDataset are out of sync of the Flytesnacks example.

What changes were proposed in this pull request?

Fix code lines to align code snippets.

Screenshots

For example, the following import is missed:

from typing_extensions import Annotated

• StructuredDataset
  

• Flytesnacks example
  

Docs link

https://flyte--5874.org.readthedocs.build/en/5874/user_guide/data_types_and_io/structureddataset.html

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.71%. Comparing base (bdaf79f) to head (80cb84a).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5874   +/-   ##
=======================================
  Coverage   36.71%   36.71%           
=======================================
  Files        1304     1304           
  Lines      130081   130081           
=======================================
  Hits        47764    47764           
  Misses      78147    78147           
  Partials     4170     4170           

Flag	Coverage Δ
unittests-datacatalog	51.58% <ø> (ø)
unittests-flyteadmin	54.41% <ø> (ø)
unittests-flytecopilot	11.73% <ø> (ø)
unittests-flytectl	62.40% <ø> (ø)
unittests-flyteidl	6.89% <ø> (ø)
unittests-flyteplugins	53.62% <ø> (ø)
unittests-flytepropeller	42.84% <ø> (ø)
unittests-flytestdlib	54.78% <ø> (ø)

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