Bump google/cloud-sdk in /dockerfiles/integration-test-runner-beta

Bumps google/cloud-sdk from 577.0.0-slim to 588.0.0-slim.

---
updated-dependencies:
- dependency-name: google/cloud-sdk
  dependency-version: 588.0.0-slim
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

dockerfiles/integration-test-runner-beta/Dockerfile

@@ -10,7 +10,7 @@ FROM mikefarah/yq:4.53.3 AS yq
 # Use FROM gcloud-sdk instead of FROM golang because its
 # a lot easier to install Go than to install gcloud in the
 # subsequent commands below.
-FROM google/cloud-sdk:577.0.0-slim
+FROM google/cloud-sdk:588.0.0-slim
 
 # Install apache2-utils (for htpasswd to bcrypt passwords for the
 # local-user-authenticator) and jq.