["DEPR"] Certificates, Auth and Util backends

**Description**
We should remove the backends and the configuration we are not using.

I propose to remove the following:
- eox_tenant.edxapp_wrapper.backends.certificates_module_i_v1
- eox_tenant.edxapp_wrapper.backends.edx_auth_n_v1
- eox_tenant.edxapp_wrapper.backends.util_h_v1

And its settings. Checking that we will not break the plugin because we are no longer using it.


