Scale up gorouters in `prod` (IE) from 3 to 6
Scale up gorouters in `prod` (IE) from 3 to 6

A tenant is doing load testing on June 10/11, this is commit scales up
the routers for this event

Signed-off-by: Toby Lorne <527052641d65eef236eeef9545b2acac74c35d57@digital.cabinet-office.gov.uk>

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