deploy/deploy.yaml: remove steps involving the beta environment

The beta environment is no longer being actively used. Keeping steps
related to deploying and testing the beta environment as part of the
main Cloud Build deployment file is therefore irrelevant, and might
cause confusion should these steps fail.

Change-Id: I061414d4edc10c4f5d68e4f24ce018238767f20c
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/714460
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Jonathan Amsterdam <[email protected]>
Reviewed-by: Nicholas Husin <[email protected]>
kokoro-CI: kokoro <[email protected]>

Author: nicholashusin

deploy/deploy.yaml

@@ -85,17 +85,6 @@ steps:
     entrypoint:  deploy/pagecheck.sh
     args:
       - prod
-  - id: Frontend - beta
-    name: gcr.io/cloud-builders/gcloud
-    entrypoint: sh
-    args:
-      - -c
-      - deploy/frontend.sh beta gcr.io/$PROJECT_ID/frontend:$(cat _BUILD_TAG)
-  - id: Pagecheck - beta
-    name: golang:1.24
-    entrypoint:  deploy/pagecheck.sh
-    args:
-      - beta
 artifacts:
   objects:
     location: 'gs://$PROJECT_ID/screentest-artifacts'