deploy: update PostValidate step to go1.20

New dependency go.opentelemetry.io/otel/sdk/metric@v1.21.0 requires go1.20.

Change-Id: I45aa7cfe9dcfa4ef7b8209344f024e8ca78a46a4
Reviewed-on: https://go-review.googlesource.com/c/vulndb/+/553495
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/deploy/build.yaml b/deploy/build.yaml
index f942911..44f5905 100644
--- a/deploy/build.yaml
+++ b/deploy/build.yaml
@@ -66,7 +66,7 @@
       - mkdir /workspace/deployed && gsutil -q -m cp -r gs://go-vulndb /workspace/deployed
 
   - id: PostValidate
-    name: golang:1.19.2
+    name: golang:1.20.12
     entrypoint: bash
     args: ["-ec", "go run ./cmd/checkdb -v1 -legacy /workspace/deployed/go-vulndb"]
     env: