CLN: remove unnecessary name in stack_arrays
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

@jorisvandenbossche any clues on the new arrow breakage? numpy 1.20 is incompatible with pyarrow < 3.0 if installed with wheels. I would need to look in the exact details of how the environment is created to check how to solve it though. But in general builds with older pyarrow should also have older (<1.20) numpy. lgtm pls rebase