Bump paas-billing v0.37.0
Bump paas-billing v0.37.0

paas-billing v0.37.0 fixes an issue with UPDATE events that alter plan
guids of services.

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