Cloud Build: Tweak timeouts. (#11763)

Co-authored-by: Marco Ebert <[email protected]>

Author: k8s-infra-cherrypick-robot

images/opentelemetry/cloudbuild.yaml

@@ -11,4 +11,4 @@ steps:
     args:
       - -c
       - gcloud auth configure-docker && cd images/opentelemetry && make NGINX_VERSION=1.21.6 push && make NGINX_VERSION=1.25.3 push
-timeout: 3600s
+timeout: 1800s