Update Helm chart NOTES.txt with newer documentation links (#8586)

This commit updates the NOTES.txt file of the Helm chart with updated
documentation links, and rephrases the text for consistency.

The release notes were changes to a changelog, and the steps for
upgrading NGINX Ingress Controller were put into their own standalone
document some time ago.

Each "outdated" link has a HTTPS redirect to the latest version: these
changes are for consistency and clarity at source.

Signed-off-by: Alan Dooley <[email protected]>

Author: ADubhlaoich

charts/nginx-ingress/templates/NOTES.txt

@@ -1,13 +1,13 @@
 NGINX Ingress Controller {{ .Chart.AppVersion }} has been installed.
 
-For release notes for this version please see: https://docs.nginx.com/nginx-ingress-controller/releases/
+For release notes, see: https://docs.nginx.com/nginx-ingress-controller/changelog/
 
-Installation and upgrade instructions: https://docs.nginx.com/nginx-ingress-controller/install/helm/
+For Helm installation instructions, see: https://docs.nginx.com/nginx-ingress-controller/install/helm/
 
 {{ if .Release.IsUpgrade -}}
 If you are upgrading from a version of the chart that uses older Custom Resource Definitions (CRD) it is necessary to manually upgrade the CRDs as this is not managed by Helm.
 To update to the latest version of the CRDs:
   $ kubectl apply -f https://raw.githubusercontent.com/nginx/kubernetes-ingress/v{{ .Chart.AppVersion }}/deploy/crds.yaml
 
-More details on upgrading the CRDs: https://docs.nginx.com/nginx-ingress-controller/install/helm#upgrading-the-crds
+For more details on upgrading the CRDs, see: https://docs.nginx.com/nginx-ingress-controller/install/upgrade/#upgrade-nginx-ingress-controller-crds
 {{- end -}}