Document clarifying notes about the data lifecycle

[popojk]

Tracking issue

Closes #4683

Why are the changes needed?

1. The Understand How Flyte Handles Data doc is lacking information about deleting raw data in storage service such as s3 and gcs.
2. Some example code in the doc is incorrect. The workflow called a function 'task_read_and_shuffle_file', but the function is not defined in example code.

What changes were proposed in this pull request?

1. Add information about raw data deletion in the doc.
2. Fix example code.

Check all the applicable boxes

• I updated the documentation accordingly.
• All commits are signed-off.

Docs link

https://flyte--5921.org.readthedocs.build/en/5921/user_guide/concepts/main_concepts/data_management.html

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.84%. Comparing base (1279740) to head (3d88187).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5921      +/-   ##
==========================================
+ Coverage   36.53%   36.84%   +0.31%     
==========================================
  Files        1249     1309      +60     
  Lines      128230   130967    +2737     
==========================================
+ Hits        46847    48259    +1412     
- Misses      77346    78524    +1178     
- Partials     4037     4184     +147     

Flag	Coverage Δ
unittests-datacatalog	51.58% <ø> (?)
unittests-flyteadmin	54.14% <ø> (ø)
unittests-flytecopilot	11.73% <ø> (ø)
unittests-flytectl	62.40% <ø> (ø)
unittests-flyteidl	6.92% <ø> (ø)
unittests-flyteplugins	53.64% <ø> (ø)
unittests-flytepropeller	43.00% <ø> (ø)
unittests-flytestdlib	55.41% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.