[SPARK-15031][EXAMPLES][FOLLOW-UP] Make Python param example working with SparkSession

## What changes were proposed in this pull request?

It seems most of Python examples were changed to use SparkSession by https://github.com/apache/spark/pull/12809. This PR said both examples below:

- `simple_params_example.py`
- `aft_survival_regression.py`

are not changed because it dose not work. It seems `aft_survival_regression.py` is changed by https://github.com/apache/spark/pull/13050 but `simple_params_example.py` is not yet.

This PR corrects the example and make this use SparkSession.

In more detail, it seems `threshold` is replaced to `thresholds` here and there by https://github.com/apache/spark/commit/5a23213c148bfe362514f9c71f5273ebda0a848a. However, when it calls `lr.fit(training, paramMap)` this overwrites the values. So, `threshold` was 5 and `thresholds` becomes 5.5 (by `1 / (1 + thresholds(0) / thresholds(1)`).

According to the comment below. this is not allowed, https://github.com/apache/spark/blob/354f8f11bd4b20fa99bd67a98da3525fd3d75c81/mllib/src/main/scala/org/apache/spark/ml/classification/LogisticRegression.scala#L58-L61.

So, in this PR, it sets the equivalent value so that this does not throw an exception.

## How was this patch tested?

Manully (`mvn package -DskipTests && spark-submit simple_params_example.py`)

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #13135 from HyukjinKwon/SPARK-15031.