Prove the untouched environment is the same map, not an equal one

internal/catalogue/port_into_test.go

@@ -162,7 +162,9 @@ func TestAContainerWithNoPortPlaceholderKeepsItsEnvironment(t *testing.T) {
 	if got := sidecar["env"].(map[string]any)["MESH_GITEA_URL"]; got != "http://gitea:3000" {
 		t.Fatalf("an address on the runtime's own network was moved to the machine's port: %v", got)
 	}
-	if !reflect.DeepEqual(sidecar["env"], env) {
+	// The same map, not a copy of it: a container that asks for nothing is left alone, and
+	// comparing the contents would say yes even to a rebuilt map.
+	if reflect.ValueOf(sidecar["env"]).Pointer() != reflect.ValueOf(env).Pointer() {
 		t.Fatalf("a container that asked for nothing had its environment rebuilt: %v", sidecar["env"])
 	}
 }