[hotfix] Fix finding buckets error in Bucketizer

[mumuhhh]

What is the purpose of the change

• Fix finding buckets error in Bucketizer

Brief change log

• Changed inputCols to splits in Bucketizer and updated the corresponding unit test.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @public(Evolving): (no)
• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (Java doc)

[zhipeng93]

Thanks for the fix @mumuhhh ! LGTM.

Two minor comments:

• Could you add a unit test that the number of inputCols is not the same as number splits?
• Could you re-polish the commit message, such as [hotfix] Fix finding buckets error in Bucketizer?

[zhipeng93]

Thanks for the fix @mumuhhh ! Merged :)