…rapidsai#2212)

Contributes to rapidsai/build-planning#242

Modifying `ci/build_wheel_python.sh` to avoid passing `--build-constraint` and `--no-build-isolation` together which results in an error from `pip`, however we want to keep environment variable `PIP_CONSTRAINT` set unconditionally.

Can be merged after rapidsai/gha-tools#237

Authors:
  - Mike McCarty (https://github.com/mmccarty)

Approvers:
  - James Lamb (https://github.com/jameslamb)

URL: rapidsai#2212

…#2214)

#2212 was into `main` after `main` had already been updated to RAPIDS
26.04.

This change is intended for RAPIDS 26.02, so this PR backports it to the
`release/26.02` branch.

## Notes for Reviewers

### How this should be merged

I think normal squash and merge should be fine? The commit SHA is
different because of the direction of the `cherry-pick` anyway.

### How I made this branch

```shell
git checkout main
git pull upstream main
git fetch upstream release/26.02
git checkout release/26.02
git checkout -b pip-changes
git cherry-pick f380eff
```

Co-authored-by: Mike McCarty <mmccarty@nvidia.com>