[MINOR][PYTHON][DOCS] Fix the type hint for extract, date_part and datepart

[zhengruifeng]

What changes were proposed in this pull request?

Fix the type hint for extract, date_part and datepart

Why are the changes needed?

argument field never supports column name:

In [6]: df = spark.createDataFrame([(datetime.datetime(2015, 4, 8, 13, 8, 15), "YEAR",)], ['ts', 'field'])

In [7]: df.select(sf.extract("field", "ts"))

...


AnalysisException: [NON_FOLDABLE_ARGUMENT] The function `extract` requires the parameter `field` to be a foldable expression of the type "STRING", but the actual argument is a non-foldable. SQLSTATE: 42K08

Does this PR introduce any user-facing change?

yes, doc only change

How was this patch tested?

ci

Was this patch authored or co-authored using generative AI tooling?

no

[zhengruifeng]

merged to master