Revert "Cache files created by (specially designed) annotation processors."

This reverts commit e556eaa08f9c8e1be64a694d739283235d6989b0.

Apparently, this fails in CI for reasons I don't understand, so I'm
reverting it until I can figure it out.
Sync of https://github.com/pantsbuild/pants/commit/0f59c73b408825dd8b25b7e94eb9fe07606cdf05