Sentry Errors::MissingSalesforceAccountIdError

Summary

We get a large amount of these errors in Sentry and we should investigate it and fix it: https://sentry.gitlab.net/gitlab/customersgitlabcom/issues/810657

@rdavila Believes it is related to worker SyncGitlabGroupMemberWorker, which is used to update Salesforce when a user is added so that Support can understand what level of support to provide to a user.

Steps

• Delete the system hook(s) that points to https://customers.gitlab.com/gitlab_system_hook from GL.com
• Drop logic related to SyncGitlabGroupMemberWorker from customers (routes / controllers / job)
• Clean up of other changes that were introduced to allow the dropped logic (this will simplify the code)
• Submit a MR to the cookbooks to remove the generation of the constant: https://gitlab.com/gitlab-cookbooks/cookbook-customers-gitlab-com/-/merge_requests/104
• Create an issue for infrastructure to drop the value: https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/11569