Checkmk Werk 15558: Drop ancient mk_oracle_dbuser.conf

ID: 15558 Title: Drop ancient mk_oracle_dbuser.conf Component: agents Level: 1 Class: Bug fix Version: 2.3.0b1 With this werk, we drop the compatibilty of using a "mk_oracle_dbuser.conf" for mk_oracle. This configuration file is actually deprecated since 2014, so we assume nobody is using it anymore.