Bump golang in /integration/cloudbuild/testbase

Bumps golang from `a0b3bc4` to `114b9cc`.

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

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

integration/cloudbuild/testbase/Dockerfile

@@ -1,5 +1,5 @@
 # This Dockerfile builds a base image for Trillan integration tests.
-FROM golang:1.21.1-bookworm@sha256:a0b3bc435cf2118e62db49d611bcdfa87a525be6fdf49179a5c9dbd4d0f1c63f
+FROM golang:1.21.1-bookworm@sha256:9c7ea4a4924ae24913401af45c9b6f439d0f782267584738d1cc1099d8b7a02c
 
 WORKDIR /testbase