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

(cherry picked from commit 4e739331187f2acdd84a5e65857edb62e58a0f8f)
Signed-off-by: Nick Pentreath <6fe12bfdafd6d3c41da5ad6593c53ed449c85282@za.ibm.com>

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