[Chore](util) remove some unused code on var_int.h

[BiteTheDDDDt]

What problem does this PR solve?

remove some unused code on var_int.h

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[hello-stephen]

Thank you for your contribution to Apache Doris.
Don't know what should be done next? See How to process your PR.

Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[BiteTheDDDDt]

run buildall

[BiteTheDDDDt]

run buildall

[BiteTheDDDDt]

run buildall

[BiteTheDDDDt]

run buildall

[hello-stephen]

BE UT Coverage Report

Increment line coverage 96.97% (32/33) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	57.19% (15399/26925)
Line Coverage	46.24% (139755/302244)
Region Coverage	45.52% (70810/155569)
Branch Coverage	40.24% (37309/92706)

[github-actions]

PR approved by anyone and no changes requested.

[zhangstar333]

maybe need this default to return false

[BiteTheDDDDt]

这里还不能return false，因为原本有一些其他类型在switch里，比如date类型trunc秒单位，实际上是什么都不做直接返回

[github-actions]

PR approved by at least one committer and no changes requested.