Bump fluxcd/notification-controller to latest release

Author: eks-distro-pr-bot

UPSTREAM_PROJECTS.yaml

@@ -117,8 +117,8 @@ projects:
             go_version: "1.25"
       - name: notification-controller
         versions:
-          - tag: v1.7.5
-            go_version: "1.25"
+          - tag: v1.8.1
+            go_version: "1.26"
       - name: source-controller
         versions:
           - tag: v1.7.4

projects/fluxcd/notification-controller/GIT_TAG

@@ -1 +1 @@
-v1.7.5
+v1.8.1

projects/fluxcd/notification-controller/GOLANG_VERSION

@@ -1 +1 @@
-1.25
+1.26

projects/fluxcd/notification-controller/README.md

@@ -1,5 +1,5 @@
 ## **Notification Controller**
-![Version](https://img.shields.io/badge/version-v1.7.5-blue)
+![Version](https://img.shields.io/badge/version-v1.8.1-blue)
 ![Build Status](https://codebuild.us-west-2.amazonaws.com/badges?uuid=eyJlbmNyeXB0ZWREYXRhIjoiVDhSNCt1djNtRytnWTgvQ01BMW13b2Y1YmZPakRrSGlRWitKZ0ZLZUdaS2xxclpLOFNidnBHNjBFWjRueHpOaGRrMzV5OUhLLzhRWHgyaC85R2tET2JZPSIsIml2UGFyYW1ldGVyU3BlYyI6IlZpNGwrazFrZndNMWE4cTciLCJtYXRlcmlhbFNldFNlcmlhbCI6MX0%3D&branch=main)
 
 The [notification-controller](https://github.com/fluxcd/notification-controller) is a Kubernetes operator specialized in handling inbound and outbound events. The controller exposes an HTTP endpoint for receiving events from other controllers. It can be configured with Kubernetes custom resources such as `Alert`, `Event`,`Provider` and `Receiver` to define how events are processed and where to dispatch them.
@@ -15,7 +15,7 @@ about changes necessary to eks-anywhere to support the new version and/or automa
 eks-anywhere version reach out to @jiayiwang7 or @danbudris
 1. Update the `GIT_TAG` file to have the new desired version based on the upstream release tags.
 1. Compare the old tag to the new, looking specifically for Makefile changes. 
-ex: [v1.2.2 compared to v1.7.5](https://github.com/fluxcd/notification-controller/compare/v1.2.2...v1.2.3). Check the `manager` target for
+ex: [v1.2.2 compared to v1.8.1](https://github.com/fluxcd/notification-controller/compare/v1.2.2...v1.2.3). Check the `manager` target for
 any build flag changes, tag changes, dependencies, etc.
 1. Verify the golang version has not changed. The version specified in `go.mod` seems to be kept up to date.  There is also
 a [dockerfile](https://github.com/fluxcd/notification-controller/blob/main/Dockerfile#L5) they use for building which has it defined.