MNT: Move pooch to a test dependency

[matthewfeickert]

• Resolves pooch runtime dependency intended? #247
• Resolves Why is pooch being picked up at install time? pyhf-feedstock#21

Remove pooch as an install dependency to avoid distributing optional dependencies without user request.

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• [N/A] Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[matthewfeickert]

@conda-forge-admin, please rerender

[conda-forge-webservices]

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 (recipe) and found it was in an excellent condition.

[matthewfeickert]

Thank you for already taking actions to mitigate the failures, @h-vetinari. 🙏

[h-vetinari]

OK, this is currently some pypy variants, so let's put this in. Thanks for the issue & pr @matthewfeickert!

[matthewfeickert]

Thanks very much for fixing everything @h-vetinari, as well as for your help, information, and direction on all of this.