Refactor ApprovalRules::CreateService initializer

Currently the ApprovalRules::CreateService initializer performs changes. This is bad practice, our initializer should be configuring the object, the execute method should handle all data modifications

https://gitlab.com/gitlab-org/gitlab/-/blob/526caa76c9b984eafa9f69b00f4c449ceeea9e34/ee/app/services/approval_rules/create_service.rb#L59