Update net-contour nightly (#16692)

bumping knative.dev/net-contour 577c757...889e425:
  > 889e425 upgrade to latest dependencies (# 1304)

Signed-off-by: Knative Automation <automation@knative.team>

Author: knative-automation

third_party/contour-latest/net-contour.yaml

@@ -8,7 +8,7 @@ metadata:
     networking.knative.dev/ingress-provider: contour
     app.kubernetes.io/component: net-contour
     app.kubernetes.io/name: knative-serving
-    app.kubernetes.io/version: "20260821-577c757d"
+    app.kubernetes.io/version: "20260921-889e4253"
     serving.knative.dev/controller: "true"
 rules:
   - apiGroups: ["projectcontour.io"]
@@ -38,7 +38,7 @@ metadata:
     networking.knative.dev/ingress-provider: contour
     app.kubernetes.io/component: net-contour
     app.kubernetes.io/name: knative-serving
-    app.kubernetes.io/version: "20260821-577c757d"
+    app.kubernetes.io/version: "20260921-889e4253"
 data:
   _example: |
     ################################
@@ -111,7 +111,7 @@ metadata:
     networking.knative.dev/ingress-provider: contour
     app.kubernetes.io/component: net-contour
     app.kubernetes.io/name: knative-serving
-    app.kubernetes.io/version: "20260821-577c757d"
+    app.kubernetes.io/version: "20260921-889e4253"
 spec:
   replicas: 1
   selector:
@@ -123,14 +123,14 @@ spec:
         app: net-contour-controller
         app.kubernetes.io/component: net-contour
         app.kubernetes.io/name: knative-serving
-        app.kubernetes.io/version: "20260821-577c757d"
+        app.kubernetes.io/version: "20260921-889e4253"
     spec:
       serviceAccountName: controller
       containers:
         - name: controller
           # This is the Go import path for the binary that is containerized
           # and substituted here.
-          image: gcr.io/knative-nightly/knative.dev/net-contour/cmd/controller@sha256:32ea6e15fba5675bc04aa8eb02404b4e64ef56a0e770da467a70c8215d7bc8e0
+          image: gcr.io/knative-nightly/knative.dev/net-contour/cmd/controller@sha256:bb5a42848f72978750e57b1eb8c47775fce11b3d64bd7af9f086ba31173e125b
           resources:
             requests:
               cpu: 40m
@@ -174,7 +174,7 @@ metadata:
     networking.knative.dev/ingress-provider: contour
     app.kubernetes.io/component: net-contour
     app.kubernetes.io/name: knative-serving
-    app.kubernetes.io/version: "20260821-577c757d"
+    app.kubernetes.io/version: "20260921-889e4253"
 spec:
   delegations:
     - secretName: routing-serving-certs