Bump golang from 1.21.3-bookworm to 1.21.4-bookworm in /integration (#…

…1234)

Bumps golang from 1.21.3-bookworm to 1.21.4-bookworm.

---
updated-dependencies:
- dependency-name: golang
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

integration/Dockerfile

@@ -1,6 +1,6 @@
 # This Dockerfile builds a base image for the certificate-transparency-go CloudBuild integration testing.
 # See https://hub.docker.com/_/golang for the set of golang base images.
-FROM golang:1.21.3-bookworm@sha256:5bafbbb109f02aaf6b41ddc19f54919773c3006f1cbda1599112603367642f0e as ct_testbase
+FROM golang:1.21.4-bookworm@sha256:85aacbed94a248f792beb89198649ddbc730649054b397f8d689e9c4c4cceab7 as ct_testbase
 
 WORKDIR /testbase