fix(ci): add missing env var (vectordotdev#17872)

Author: neuronull

.github/workflows/integration-comment.yml

@@ -31,6 +31,7 @@ env:
   AWS_SECRET_ACCESS_KEY: "dummy"
   AXIOM_TOKEN: ${{ secrets.AXIOM_TOKEN }}
   TEST_APPSIGNAL_PUSH_API_KEY: ${{ secrets.TEST_APPSIGNAL_PUSH_API_KEY }}
+  TEST_DATADOG_API_KEY: ${{ secrets.CI_TEST_DATADOG_API_KEY }}
   CONTAINER_TOOL: "docker"
   DD_ENV: "ci"
   DD_API_KEY: ${{ secrets.DD_API_KEY }}