Merge pull request #6212 from kubernetes/towca-patch-1

Update image builder to use Go 1.21.3

Author: k8s-ci-robot

builder/Dockerfile

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM golang:1.20.4
+FROM golang:1.21.3
 LABEL maintainer="Marcin Wielgus <mwielgus@google.com>"
 
 ENV GOPATH /gopath/