[SPARK-15444][PYSPARK][ML][HOTFIX] Default value mismatch of param...

[SPARK-15444][PYSPARK][ML][HOTFIX] Default value mismatch of param linkPredictionCol for GeneralizedLinearRegression

## What changes were proposed in this pull request?

Default value mismatch of param linkPredictionCol for GeneralizedLinearRegression between PySpark and Scala. That is because default value conflict between #13106 and #13129. This causes ml.tests failed.

## How was this patch tested?
Existing tests.

Author: Liang-Chi Hsieh <simonh@tw.ibm.com>

Closes #13220 from viirya/hotfix-regresstion.