Update documentation to point M1 users at install.sh.
Update documentation to point M1 users at install.sh.

https://github.com/deepmind/meltingpot/issues/46

PiperOrigin-RevId: 456245065
Change-Id: I56456a30747e17494eafcd5e2e64beccc8133886

deepmind/meltingpot,deepmind/meltingpot