docs: Update dml_handlers module docs (#7194)

Update the module diagram to reflect kafkaless
changes.

Co-authored-by: Dom <dom@itsallbroken.com>

router/src/dml_handlers/mod.rs

@@ -33,7 +33,7 @@
 //!                                   │
 //!                                   │
 //!                          ┌────────▼─────┐
-//!                          │    Kafka     ├┐
+//!                          │  Ingester2   ├┐
 //!                          └┬─────────────┘├┐
 //!                           └┬─────────────┘│
 //!                            └──────────────┘