fix: use official kubectl image for gateway API CRD installer job (#514)

bitnami/kubectl:1.31.4 tag does not exist on Docker Hub, causing
ImagePullBackOff. Switch to the official distroless image
registry.k8s.io/kubectl:v1.31.4 and update command/args since the
distroless image has no /bin/sh.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: sanmesh-kakade

modules/gateway_api_crd/k8s/1.0/main.tf

@@ -93,11 +93,11 @@ resource "kubernetes_job_v1" "gateway_api_crd_installer" {
 
         container {
           name    = "kubectl"
-          image   = "bitnami/kubectl:1.31.4"
-          command = ["/bin/sh", "-c"]
+          image   = "registry.k8s.io/kubectl:v1.31.4"
+          command = ["kubectl"]
           args = [
             # Using --server-side to avoid annotation size limit (262KB)
-            "kubectl apply --server-side -f ${local.install_url}"
+            "apply", "--server-side", "-f", local.install_url
           ]
         }
       }