Missed globalisation of one LDAP envvar due to mistyping

[mmattel]

Based on the chat in matrix and a discussion with @rhafer:

We missed to "migrate" one LDAP_ envvar to the OCIS_ namespace.

This was due the fact that
LDAP_USER_SCHEMA_DISPLAY_NAME (graph) was named different than all the others
LDAP_USER_SCHEMA_DISPLAYNAME (groups, auth-basic, users) .

We therefore must do the following in the graph service:

• Add the global envvar OCIS_LDAP_USER_SCHEMA_DISPLAYNAME to LDAP_USER_SCHEMA_DISPLAY_NAME
• Add the local envvar LDAP_USER_SCHEMA_DISPLAYNAME to LDAP_USER_SCHEMA_DISPLAY_NAME
• Deprecate LDAP_USER_SCHEMA_DISPLAY_NAME

@micbar, this should be done asap to be part in the upcoming production release.