Disable integration tests on Windows to reduce build time

[traversaro]

Checklist

• [x] Used a personal fork of the feedstock to propose changes
• [x] Bumped the build number (if the version is unchanged)
• [ ] Reset the build number to 0 (if the version changed)
• [x] 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)
• [x] Ensured the license file is being packaged.

[conda-forge-linter]

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.

[traversaro]

@conda-forge-admin, please rerender

[github-actions[bot]]

Hi! This is the friendly automated conda-forge-webservice. I tried to rerender for you, but it looks like there was nothing to do.

[traversaro]

Turns out that it is not just to reduce time: the current strategy of just using one thread is not really robust, it worked for the PR build in https://github.com/conda-forge/libignition-physics-feedstock/pull/21 but then it failed for the post-PR build in https://dev.azure.com/conda-forge/feedstock-builds/_build/results?buildId=389657&view=logs&jobId=a70f640f-cc53-5cd3-6cdc-236a1aa90802&j=a70f640f-cc53-5cd3-6cdc-236a1aa90802&t=f5d15007-a01c-5ad8-c9ce-4d519d3b275f .