State -> Stage

Signed-off-by: Francesco Guardiani <francescoguard@gmail.com>

Author: slinkydeveloper

docs/eventing/experimental-features.md

@@ -55,7 +55,7 @@ data:
 
 **Flag name**: `delivery-timeout`
 
-**State**: Alpha, disabled by default
+**Stage**: Alpha, disabled by default
 
 **Tracking issue**: https://github.com/knative/eventing/issues/5148