Enable osx-arm64 builds by default

Now that we have native CI for osx-arm64 (#1781), which is fast becoming the most dominant architecture (c.f. #2646), we should IMO enable osx-arm64 builds by default in staged-recipes CI, thus upon feedstock-creation, and finally come up with a plan how to get rid of the osx-arm64 [migrator](https://conda-forge.org/status/migration/?name=armosxaddition) (i.e. that new feedstocks have to add themselves to [this file](https://github.com/conda-forge/conda-forge-pinning-feedstock/blob/main/recipe/migration_support/osx_arm64.txt)).