chore(deps): update ghcr.io/fluxcd/notification-controller docker tag to v1.7.3

Author: renovate[bot]

clusters/my-cluster/flux-system/gotk-components.yaml

@@ -12331,7 +12331,7 @@ spec:
             resourceFieldRef:
               containerName: manager
               resource: limits.memory
-        image: ghcr.io/fluxcd/notification-controller:v1.4.0
+        image: ghcr.io/fluxcd/notification-controller:v1.7.3
         imagePullPolicy: IfNotPresent
         livenessProbe:
           httpGet: