OBSDOCS-1737: Provide examples of configuring retention in TempoStack

Signed-off-by: Pavol Loffay <p.loffay@gmail.com>

modules/distr-tracing-tempo-config-default.adoc

@@ -19,7 +19,10 @@ spec: # <5>
   storage: {} # <6>
   resources: {} # <7>
   replicationFactor: 1 # <8>
-  retention: {} # <9>
+  retention: # <9>
+    global:
+      traces: 48h
+    perTenant: {}
   template:
       distributor: {} # <10>
       ingester: {} # <11>
@@ -46,7 +49,7 @@ spec: # <5>
 <6> Storage is specified at instance deployment. See the installation page for information about storage options for the instance.
 <7> Defines the compute resources for the Tempo container.
 <8> Integer value for the number of ingesters that must acknowledge the data from the distributors before accepting a span.
-<9> Configuration options for retention of traces.
+<9> Configuration options for retention of traces. The default value is `48h`.
 <10> Configuration options for the Tempo `distributor` component.
 <11> Configuration options for the Tempo `ingester` component.
 <12> Configuration options for the Tempo `compactor` component.