CLN: Returned dtype of _get_cython_function unused

[WillAyd]

Minor code cleanup opportunity here. _get_cython_function in core/groupby returns a tuple containing a function and a dtype_str. While the latter is unpacked, it never appears to be used in code that calls it.

pandas/pandas/core/groupby.py

Line 2243 in 93c86aa

return func, dtype_str

As an alternate to removing it, it may serve some purpose if the below line is refactored to use it rather than creating its own local variable, but unless there's some other purposes I'd still just suggest cleaning up the _get_cython_function itself

pandas/pandas/core/groupby.py

Line 2318 in 93c86aa

out_dtype = '%s%d' % (values.dtype.kind, values.dtype.itemsize)

[jreback]

cleaning welcome! yeah the dtype_str is prob not needed