ci(appengine): add metadata/standard to testing isolation

Author: glasnt

.github/config/nodejs-prod.jsonc

@@ -70,7 +70,6 @@
     "ai-platform/snippets", // PERMISSION_DENIED: Permission denied: Consumer 'projects/undefined' has been suspended.
     "appengine/analytics", // [ERR_REQUIRE_ESM]: require() of ES Module
     "appengine/metadata/flexible", // [ERR_REQUIRE_ESM]: require() of ES Module
-    "appengine/metadata/standard", // [ERR_REQUIRE_ESM]: require() of ES Module
     "automl", // (untested) FAILED_PRECONDITION: Google Cloud AutoML Natural Language was retired on March 15, 2024. Please migrate to Vertex AI instead
     "cloud-sql/mysql/mysql", // (untested) Error: expected 200 "OK", got 500 "Internal Server Error"
     "cloud-sql/mysql/mysql2", // (untested) Error: Cannot find module './connect-connector-with-iam-authn.js'

appengine/metadata/ci-setup.json

@@ -0,0 +1,3 @@
+{
+    "node-version": 20
+  }