BUG: 1.5rc raises TypeError when passing tuple to series.str.startswith()

[janosh]

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Reproducible Example

import pandas as pd

df = pd.util.testing.makeMixedDataFrame()

df.C.str.startswith(("a", "b"))

Issue Description

Example works as expected in 1.4.4. After pip install --upgrade --pre pandas==1.5.0rc0, the same code raises

TypeError: expected a string object, not tuple

stack trace

      1 import pandas as pd
      3 df = pd.util.testing.makeMixedDataFrame()
----> 5 df.C.str.startswith(("a", "b"))

File ~/.venv/py310/lib/python3.10/site-packages/pandas/core/strings/accessor.py:129, in forbid_nonstring_types.<locals>._forbid_nonstring_types.<locals>.wrapper(self, *args, **kwargs)
    124     msg = (
    125         f"Cannot use .str.{func_name} with values of "
    126         f"inferred dtype '{self._inferred_dtype}'."
    127     )
    128     raise TypeError(msg)
--> 129 return func(self, *args, **kwargs)

File ~/.venv/py310/lib/python3.10/site-packages/pandas/core/strings/accessor.py:2345, in StringMethods.startswith(self, pat, na)
   2343 if not isinstance(pat, str):
   2344     msg = f"expected a string object, not {type(pat).__name__}"
-> 2345     raise TypeError(msg)
   2346 result = self._data.array._str_startswith(pat, na=na)
   2347 return self._wrap_result(result, returns_string=False)

TypeError: expected a string object, not tuple

I guess the ability to pass tuples was never documented? #38281

Expected Behavior

Should return boolean series.

Installed Versions

INSTALLED VERSIONS

commit : 224458e
python : 3.10.6.final.0
python-bits : 64
OS : Darwin
OS-release : 21.6.0
Version : Darwin Kernel Version 21.6.0: Wed Aug 10 14:28:23 PDT 2022; root:xnu-8020.141.5~2/RELEASE_ARM64_T6000
machine : arm64
processor : arm
byteorder : little
LC_ALL : None
LANG : None
LOCALE : None.UTF-8

pandas : 1.5.0rc0
numpy : 1.23.2
pytz : 2022.1
dateutil : 2.8.2
setuptools : 63.2.0
pip : 22.1
Cython : 0.29.26
pytest : 7.1.2
hypothesis : 6.42.0
...
xlrd : 2.0.1
xlwt : 1.3.0
zstandard : None
tzdata : None

[CloseChoice]

Label this as regression for now. Would argue that we should document and support handing tuples to Series.str.startswith since this behaviour is there at least from Dec 2020 (see issue #38281) on.

[janosh]

I think it should also count as a regression for the reason that the docs claim it's equivalent to str.startswith() which does support tuples:

pandas/pandas/core/strings/accessor.py

Lines 2293 to 2297 in 54347fe

	Test if the start of each string element matches a pattern.
	Equivalent to :meth:`str.startswith`.
	Parameters