Update confirm buttons colours for addons and subscription purchase flow

Problem

For all the purchase flows (Subscription, CI Minutes, Storage) on GitLab we should use consistent colors for buttons on every step.

Current UX

All other confirmation buttons Zuora iframe button
Screenshot_2023-01-04_at_16.14.27 Screenshot_2023-01-04_at_16.14.04

Proposal

As we have deprecated the success (green) buttons in Pajamas, we should update them all to be the primary blue button.

Edited by Diana Zubova