Attempt noarch_platforms build

[willGraham01]

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.

Do not merge until cellfinder-core version is updated (see this checklist)

• Waiting on Update README in light of possible noarch build brainglobe/cellfinder-core#191
• Waiting on PyPI upload of cellfinder-core with Forbid import when tensorflow is not installed brainglobe/cellfinder-core#186 changes

Once ready:

• Closes [BUG?] Versions >=0.4.0 cannot be installed using only conda-forge channels #13

As suggested in #13, we can try to make use of noarch_platforms builds to ship a functional package on as many OSes as possible.

Currently only Windows has the tensorflow incompatibility issue, unix operating systems appear to be able to fetch tensorflow just fine. So we can specify a "unix-only" dependency of tensorflow, which should allow us to ship a working package on those platforms.

Windows installs will retain a broken package though. Also all the final checks can only pass on unix for the same reason, so they've been scoped to unix only.

[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.

[willGraham01]

@conda-forge-admin please rerender

[adamltyson]

LGTM

[willGraham01]

@adamltyson can you hit merge? I don't have write access to this repo as I'm not a maintainer