fix(k8s): use correct targets for Docker image build (#1709)

* Update kubernetes.md

The Dockerfile in current version calls the targets `app_php` and `app_caddy`, I don't know where the `pwa` part is anymore.

* Update deployment/kubernetes.md

---------

Co-authored-by: Alan Poulain <contact@alanpoulain.eu>

Author: brettins

deployment/kubernetes.md

@@ -36,9 +36,9 @@ If you do not have gcloud yet, install it with these command.
 Versioning: The 0.1.0 is the version. This value should be the same as the attribute `appVersion` in `Chart.yaml`.
 Infos for [Google Container pulling and pushing](https://cloud.google.com/container-registry/docs/pushing-and-pulling)
 
-    docker build -t gcr.io/test-api-platform/php:0.1.0 -t gcr.io/test-api-platform/php:latest api --target api_platform_php
-    docker build -t gcr.io/test-api-platform/caddy:0.1.0 -t gcr.io/test-api-platform/caddy:latest api --target api_platform_caddy
-    docker build -t gcr.io/test-api-platform/pwa:0.1.0 -t gcr.io/test-api-platform/pwa:latest pwa --target api_platform_pwa_prod
+    docker build -t gcr.io/test-api-platform/php:0.1.0 -t gcr.io/test-api-platform/php:latest api --target app_php
+    docker build -t gcr.io/test-api-platform/caddy:0.1.0 -t gcr.io/test-api-platform/caddy:latest api --target app_caddy
+    docker build -t gcr.io/test-api-platform/pwa:0.1.0 -t gcr.io/test-api-platform/pwa:latest pwa --target prod
 
 #### 2. Push your images to your Docker registry