Revert ".travis.yml: Add aarch64-apple-darwin builds"
Revert ".travis.yml: Add aarch64-apple-darwin builds"

Reverting this for now until I can figure out how to get Travis to
produce Apple Silicon builds.

This reverts commit eeeedde97229e4fde86fd25cdae33ed384401568.

rschmitt/heatseeker,rschmitt/heatseeker