Tempo 3 removed the ingester (the live-store and block-builder replace
it) and refuses to start on a config that still has an `ingester:`
block ("field ingester not found in type app.Config"). The block, three
tuning values, is dropped; Tempo 3's defaults take over.
Verified with grafana/tempo:3.1.1 on this config: /ready answers, and a
span posted over OTLP/HTTP comes back from /api/v2/traces/<id> within
10 seconds.