Add more Google machine types

[christopheredsall]

I've had a hard time booting any of the larger shapes in europe-west4-{b,c}

• n1-standard-96
• c2-standard-30
• c2-standard-60

So I've left them off for the moment

The c2-* shapes won't actually work until https://github.com/ACRC/slurm-ansible-playbook/issues/66 is resolved

[milliams]

This is no longer needed as we moved to generating the list of node types dynamically last year.