MAINT: Add warning filter for `np.long`
Hi!
This is a one-line follow-up PR after https://github.com/pandas-dev/pandas/pull/55369.
Downstream libs that use nightly pandas and numpy will see a warning without it (there was a similar fix for scipy: https://github.com/scipy/scipy/pull/19341). 
Hello (again) and thanks for this PR. I am seeing the warning but this time from `pandas` instead of `scipy`.

https://github.com/pandas-dev/pandas/blob/06cdcc0576e387551462511f82d3eed8c02be570/pandas/compat/numpy/__init__.py#L29

Example log: https://github.com/spacetelescope/jdaviz/actions/runs/6407816486/job/17396675526?pr=2492 Great thanks @mtsokol  Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

```
git checkout 2.1.x
git pull
```

2. Cherry pick the first parent branch of the this PR on top of the older branch:
```
git cherry-pick -x -m1 eb6317a3cf45dfeb76f81655310604de029ad596
```

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

```
git commit -am 'Backport PR #55397: MAINT: Add warning filter for `np.long`'
```

4. Push to a named branch:

```
git push YOURFORK 2.1.x:auto-backport-of-pr-55397-on-2.1.x
```

5. Create a PR against branch 2.1.x, I would have named this PR:

> "Backport PR #55397 on branch 2.1.x (MAINT: Add warning filter for `np.long`)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the `Still Needs Manual Backport` label once the PR gets merged.

If these instructions are inaccurate, feel free to [suggest an improvement](https://github.com/MeeseeksBox/MeeseeksDev).
                 @meeseeksdev backport 2.1.x