docs: discourage freezing default values in user values.yaml (fix #16523)

Users sometimes copy‑paste the entire default `values.yaml` into their own configs, which “freezes” all defaults
and prevents them from inheriting new defaults in future chart versions.

This change enhances the Helm chart documentation to emphasize that:
- Only *overridden* fields should be declared by users.
- Avoid duplicating all default values.
- Leaving fields unset allows users to benefit from upstream default updates.

These adjustments help maintain upgrade compatibility, reduce config bloat, and make it easier to adopt new defaults.

Closes: #16523

Signed-off-by: raaizik <132667934+raaizik@users.noreply.github.com>
Co-Authored-By: Travis Nielsen <tnielsen@redhat.com>
(cherry picked from commit f6c734a576)

Documentation/Helm-Charts/ceph-cluster-chart.gotmpl.md

@@ -40,6 +40,9 @@ The `release` channel is the most recent release of Rook that is considered stab
 The example install assumes you have first installed the [Rook Operator Helm Chart](operator-chart.md)
 and created your customized values.yaml.
 
+!!! tip
+   Instead of copying the entire default `values.yaml`, create a new `values.yaml` file that only includes the settings you want to override.
+
 ```console
 helm repo add rook-release https://charts.rook.io/release
 helm install --create-namespace --namespace rook-ceph rook-ceph-cluster \

Documentation/Helm-Charts/ceph-cluster-chart.md

@@ -43,6 +43,9 @@ The `release` channel is the most recent release of Rook that is considered stab
 The example install assumes you have first installed the [Rook Operator Helm Chart](operator-chart.md)
 and created your customized values.yaml.
 
+!!! tip
+   Instead of copying the entire default `values.yaml`, create a new `values.yaml` file that only includes the settings you want to override.
+
 ```console
 helm repo add rook-release https://charts.rook.io/release
 helm install --create-namespace --namespace rook-ceph rook-ceph-cluster \