disable alertmanager discovery for prometheus in ops
What
Disables alertmanager discovery for legacy ops prometheus instances
Why
We disabled alerting for old prometheus instances via gitlab-com/gl-infra/production#18117 (closed). However since we deploy alertmanager itself to the ops instance, it discovers it via the build in kubernetes service discovery.
This disables the config to bring it in line with the other instances. It does not affect alertmanagers operation.