[Engineering] Update survey response Calendly URL

Update the current URL to use the new shared event URL: https://calendly.com/d/n9wd-sy2b/gitlab-user-onboarding-research

https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/controllers/survey_responses_controller.rb#L5

@mkarampalas:

I think we should do a little testing first. Once a few more folks accept the invitation to the team we can test a few scenarios and make sure it's all working as expected.

cc @jstava @pcalder