[MINOR] Correct LogisticRegression test case for probability2prediction.

## What changes were proposed in this pull request?
Set correct column names for ```force to use probability2prediction``` in ```LogisticRegressionSuite```.

## How was this patch tested?
Change unit test.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #16477 from yanboliang/lor-pred.