[SPARK-32088][PYTHON] Pin the timezone in timestamp_seconds doctest

[GuoPhilipse]

What changes were proposed in this pull request?

Add American timezone during timestamp_seconds doctest

Why are the changes needed?

timestamp_seconds doctest in functions.py used default timezone to get expected result
For example:

>>> 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, 7, 30))]

But when we have a non-american timezone, the test case will get different test result.

For example, when we set current timezone as Asia/Shanghai, the test result will be

[Row(ts=datetime.datetime(2008, 12, 25, 23, 30))]

So no matter where we run the test case ,we will always get the expected permanent result if we set the timezone on one specific area.

Does this PR introduce any user-facing change?

No

How was this patch tested?

Unit test

[HyukjinKwon]

ok to test

[HyukjinKwon]

@GuoPhilipse, can you elaborate a bit more in the PR description about why it fails with which output?

[GuoPhilipse]

@GuoPhilipse, can you elaborate a bit more in the PR description about why it fails with which output?

sure, will improve it.

[SparkQA]

Test build #124543 has finished for PR 28932 at commit 233ac9c.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[dongjoon-hyun]

+1, LGTM. Thank you, @GuoPhilipse and @HyukjinKwon !
Merged to master.

[MaxGekk]

Actually, the SQL config spark.sql.session.timeZone is not used in PySpark collect() at all. This PR fixes the problem of running the example in a time zone different from America/Los_Angeles: #28959