Bump paas-billing to v0.30.0
Bump paas-billing to v0.30.0

paas-billing v0.30.0 updates the pricing formulas for Compose-hosted
services to calculate prices based on a fraction of the total cluster
memory usage.

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf