update loc second argument to column

[konabuta]

Changed he second argument of the loc function to specify the column instead of DataFrame - X.

Why are these changes needed?

The current implement of loc funcion is specifing dataframe which causes error when dealing with duplicated dataframe.

Related issue number

N/A

Checks

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• I've included any doc changes needed for https://microsoft.github.io/FLAML/. See https://microsoft.github.io/FLAML/docs/Contribute#documentation to build and test documentation locally.
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[Copilot]

Pull Request Overview

This PR fixes a bug in the time series duplicate detection logging where the loc function was incorrectly using the DataFrame as the second argument instead of the column name.

• Fixed incorrect pandas loc indexing syntax in duplicate timestamp logging
• Updated the warning message to properly display duplicate timestamp values

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[thinkall]

Good catch! Thank you @konabuta for the PR!