[KYUUBI #6250][FOLLOWUP] Simplify code after dropping Spark 3.1

[pan3793]

🔍 Description

As title, simplify code after dropping Spark 3.1.

Types of changes 🔖

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Test Plan 🧪

Pass GHA.

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Checklist 📝

• This patch was not authored or co-authored using Generative Tooling

Be nice. Be informative.

[pan3793]

cc @liuxiaocs7

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 57.14286% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 58.36%. Comparing base (42c619a) to head (2b52de6).
Report is 1 commits behind head on master.

Files	Patch %	Lines
...ache/kyuubi/engine/spark/schema/SchemaHelper.scala	57.14%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6277      +/-   ##
============================================
- Coverage     58.47%   58.36%   -0.11%     
  Complexity       24       24              
============================================
  Files           651      650       -1     
  Lines         39550    39543       -7     
  Branches       5449     5448       -1     
============================================
- Hits          23125    23081      -44     
- Misses        13952    13979      +27     
- Partials       2473     2483      +10     

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[liuxiaocs7]

LGTM, thanks for the reminder

[pan3793]

Merged to master