maintenance: add missing dep to grayskull pixi feature for '-u' support

[henryiii]

Signed-off-by: Henry Schreiner henryschreineriii@gmail.com

This dependency seems to be missing. Adding it lets users try out the -u flag.

[github-actions]

Hi! This is the staged-recipes linter and I found some lint.

It looks like some changes were made outside the recipes/ directory. To ensure everything runs smoothly, please make sure that recipes are only added to the recipes/ directory and no other files are changed.

If these changes are intentional (and you aren't submitting a recipe), please add a maintenance label to the PR.

File-specific lints and/or hints:

• pixi.toml:
  • lints:
    • Do not edit files outside of the recipes/ directory.

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR () and found it was in an excellent condition.