chore(deps): Tempo 2.7.2 → 3.1.1

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.

compose.yml

@@ -824,7 +824,7 @@ services:
     restart: unless-stopped
 
   tempo:
-    image: grafana/tempo:2.7.2
+    image: grafana/tempo:3.1.1
     container_name: tempo
     networks:
       - observability

infra/tempo/tempo.yml

@@ -10,10 +10,8 @@ distributor:
         http:
           endpoint: 0.0.0.0:4318
 
-ingester:
-  trace_idle_period: 30s
-  max_block_bytes: 1048576
-  max_block_duration: 5m
+# No `ingester:` block: Tempo 3 removed the ingester (its live-store and
+# block-builder replace it, on defaults), and rejects the key outright.
 
 storage:
   trace: