[docker] ignore mypy_cache everywhere (#9620)
[docker] ignore mypy_cache everywhere (#9620)

Without the ** it seems to not ignore any mypy_cache. This results in extraordinarily slow local builds.
hail-is/hail,cseed/hail,hail-is/hail,cseed/hail,danking/hail,cseed/hail,danking/hail,danking/hail,cseed/hail,hail-is/hail,danking/hail,hail-is/hail,cseed/hail,danking/hail,hail-is/hail,cseed/hail,cseed/hail,danking/hail,hail-is/hail,danking/hail,hail-is/hail,cseed/hail,hail-is/hail,danking/hail