self-managed install docs: Use unified tags instead of self-managed specific ones

Author: def-

doc/user/layouts/shortcodes/self-managed/versions/curl-sample-files-local-install.html

@@ -2,10 +2,9 @@
 {{ $environmentd_version := site.Data.self_managed.latest_versions.environmentd_version }}
 
 ```shell
-mz_operator_version=self-managed-{{ $operator_helm_chart_version}}
 mz_version={{ $environmentd_version }}
 
-curl -o sample-values.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_operator_version/misc/helm-charts/operator/values.yaml
+curl -o sample-values.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_version/misc/helm-charts/operator/values.yaml
 curl -o sample-postgres.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_version/misc/helm-charts/testing/postgres.yaml
 curl -o sample-minio.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_version/misc/helm-charts/testing/minio.yaml
 curl -o sample-materialize.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_version/misc/helm-charts/testing/materialize.yaml

doc/user/layouts/shortcodes/self-managed/versions/upgrade/upgrade-steps-local-kind.html

@@ -18,9 +18,9 @@
 1. Get the sample configuration files for the new version.
 
    ```shell
-   mz_operator_version=self-managed-{{ $operator_version }}
+   mz_version={{ $environmentd_version }}
 
-   curl -o upgrade-values.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_operator_version/misc/helm-charts/operator/values.yaml
+   curl -o upgrade-values.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_version/misc/helm-charts/operator/values.yaml
    ```
 
    If you have previously modified the `sample-values.yaml` file for your

doc/user/layouts/shortcodes/self-managed/versions/upgrade/upgrade-steps-local-minikube.html

@@ -18,9 +18,9 @@
 1. Get the sample configuration files for the new version.
 
    ```shell
-   mz_operator_version=self-managed-{{ $operator_version }}
+   mz_version={{ $environmentd_version }}
 
-   curl -o upgrade-values.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_operator_version/misc/helm-charts/operator/values.yaml
+   curl -o upgrade-values.yaml https://raw.githubusercontent.com/MaterializeInc/materialize/refs/tags/$mz_version/misc/helm-charts/operator/values.yaml
    ```
 
    If you have previously modified the `sample-values.yaml` file for your