deploy: upgrade to go 1.19beta1

This is a prerequisite for using the new go/doc/comment package.

Change-Id: I063d03f662ab385a1e90965c444f32598eef2612
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/415014
Run-TryBot: Jamal Carvalho <jamal@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Auto-Submit: Jamal Carvalho <jamal@golang.org>
diff --git a/deploy/migrate.yaml b/deploy/migrate.yaml
index ea78500..39f6c77 100644
--- a/deploy/migrate.yaml
+++ b/deploy/migrate.yaml
@@ -16,7 +16,7 @@
     args:
       - $PROJECT_ID
   - id: Migrate
-    name: golang:1.18.0
+    name: golang:1.19beta1
     entrypoint: bash
     dir: private
     args:
diff --git a/deploy/sitemap.yaml b/deploy/sitemap.yaml
index d7acaf5..5966955 100644
--- a/deploy/sitemap.yaml
+++ b/deploy/sitemap.yaml
@@ -9,7 +9,7 @@
     args:
       - $PROJECT_ID
   - id: Build
-    name: golang:1.18.0
+    name: golang:1.19beta1
     entrypoint: bash
     dir: private
     args: