### What changes were proposed in this pull request?
Modify the example for `timestamp_seconds` and replace `collect()` by `show()`.
### Why are the changes needed?
The SQL config `spark.sql.session.timeZone` doesn't influence on the `collect` in the example. The code below demonstrates that:
```
$ export TZ="UTC"
```
```python
>>> from pyspark.sql.functions import timestamp_seconds
>>> spark.conf.set("spark.sql.session.timeZone", "America/Los_Angeles")
>>> time_df = spark.createDataFrame([(1230219000,)], ['unix_time'])
>>> time_df.select(timestamp_seconds(time_df.unix_time).alias('ts')).collect()
[Row(ts=datetime.datetime(2008, 12, 25, 15, 30))]
```
The expected time is **07:30 but we get 15:30**.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
By running the modified example via:
```
$ ./python/run-tests --modules=pyspark-sql
```
Closes#28959 from MaxGekk/SPARK-32088-fix-timezone-issue-followup.
Authored-by: Max Gekk <max.gekk@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
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