Test flash calls in Projects::GoogleCloud::DatabasesController and Projects::GoogleCloud::DeploymentsController

There are flash calls in Projects::GoogleCloud::DatabasesController and Projects::GoogleCloud::DeploymentsController that aren't tested. We can increase the coverage of the specs by covering the cases.

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The following discussion from !109086 (merged) should be addressed:

• @patrickbajao started a discussion:

  We can test this in https://gitlab.com/gitlab-org/gitlab/-/blob/aeab55d53bc4c01e33dc13e4c377a41c4d6d2948/spec/requests/projects/google_cloud/deployments_controller_spec.rb and the one for databases_controller in https://gitlab.com/gitlab-org/gitlab/-/blob/aeab55d53bc4c01e33dc13e4c377a41c4d6d2948/spec/requests/projects/google_cloud/databases_controller_spec.rb.

  But since they aren't there before, I don't think it should block this MR. We can work on this as a follow up.