feat: Update r33 notice banner (#631)

This commit updates the r33 notice banner that was converted into the
new banner system with the latest theme release. The original link was a
series of nested relative links: it replaces it with a Hugo reference.

Author: ADubhlaoich

_banners/upgrade-r33.md

@@ -1,5 +1,5 @@
 {{< banner "caution" "NGINX Plus R33 requires NGINX Instance Manager 2.18 or later" >}}
   If your NGINX data plane instances are running NGINX Plus R33 or later, you must upgrade to NGINX Instance Manager 2.18 or later to support usage reporting. NGINX Plus R33 instances must report usage data to the F5 licensing endpoint or NGINX Instance Manager. Otherwise, they will stop processing traffic. 
   <br><br>
-  For more details about usage reporting and enforcement, see [About solution licenses](../../../../solutions/about-subscription-licenses)
+  For more details about usage reporting and enforcement, see [About solution licenses]({{< ref "/solutions/about-subscription-licenses.md" >}})
 {{</ banner >}}