Fix `channel_sources` upload checks

[jaimergp]

Checklist

• [X] 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 code>@<space/conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• [ ] Ensured the license file is being packaged.

Instead of checking whether the string starts with the pattern, check for a full match.

cc/ @isuruf @beckermr

[conda-forge-webservices[bot]]

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.

[beckermr]

@jaimergp shall we merge this?

[jaimergp]

If there are no comments, I guess!

[beckermr]

We need to bump the version of the ci-setup package here too. Then we can merge!

[beckermr]

Thank you!