cmd/server: remove jaeger, disable opentelemetry by default

Created by: bobheadxi

With jaeger no longer being the default tracing mechanism (https://github.com/sourcegraph/sourcegraph/pull/41242), this change removes jaeger from sourcegraph/server - it is disrecommended for production use, so I think this is probably fine - and also disables OpenTelemetry (https://github.com/sourcegraph/sourcegraph/pull/41243) in sourcegraph/server so we don't have to figure out an OpenTelemetry deployment for it (again, this image is not recommended for production use so I don't think we need to introduce advanced capabilities like OpenTelemetry out-of-the-box for it (there is some precedent for this - cAdvisor, for example, is not included in sourcegraph/server). Users can still configure an exporter with OTEL_EXPORTER_OTLP_ENDPOINT.

Docs indicating it is not recommended for production use:

Test plan

CI passes, main-dry-run: https://buildkite.com/sourcegraph/sourcegraph/builds?branch=main-dry-run/src-server-remove-jaeger