feat: Fix erroneous upgrade link (#989)

This commit fixes a production URL link in NGINX Ingress Controller's
instructions which should have been a Hugo reference shortcode.

Author: ADubhlaoich

content/includes/nic/installation/create-custom-resources.md

@@ -30,9 +30,10 @@ kubectl apply -f https://raw.githubusercontent.com/nginx/kubernetes-ingress/v{{<
 
 {{%tab name="Install CRDs after cloning the repo"%}}
 
-{{< call-out "note" >}} If you are installing the CRDs this way, ensure you have first cloned the repository. {{< /call-out >}}
+{{< call-out "note" >}} 
+
+Read the steps outlined in [Upgrade from 3.x to 4.x]({{< ref "/nic/installation/upgrade-version.md#upgrade-from-3x-to-4x" >}}) before running the CRD upgrade and perform the steps if applicable.
 
-{{< call-out "note" >}} Please make sure to read the steps outlined in [Upgrade to V4](https://docs.nginx.com/nginx-ingress-controller/installation/installing-nic/upgrade-to-v4/#update-custom-resource-apiversion) before running the CRD upgrade and perform the steps if applicable.
 {{< /call-out >}}