cmd/golangorg: update App Engine runtime to Go 1.27

By now the supported and tested Go versions are Go 1.27 and 1.26.
Update the website deployment to start using the Go 1.27 runtime.
See https://cloud.google.com/appengine/docs/standard/lifecycle/support-schedule#go.

For golang/go#72774.

Change-Id: I2384ad8007a7b6dd3635596dadfbcc2486ea71d9
Reviewed-on: https://go-review.googlesource.com/c/website/+/818440
Reviewed-by: Ethan Lee <ethanalee@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/cmd/golangorg/app.yaml b/cmd/golangorg/app.yaml
index 2b6ae6f..a563bc7 100644
--- a/cmd/golangorg/app.yaml
+++ b/cmd/golangorg/app.yaml
@@ -2,7 +2,7 @@
 # Do not deploy directly.
 
 service: default
-runtime: go125
+runtime: go127
 main: ./cmd/golangorg
 
 env_variables: