Add wgrib2 to arch rebuild

[four43]

I was sent here via conda-forge/wgrib2-feedstock#42 and am testing out the CI arm build for wgrib2.

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• 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.

[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 (recipe/meta.yaml) and found it was in an excellent condition.

[four43]

@conda-forge-admin, please rerender

(I'm actually really curious what this does)