Don't use gcr.io/bazel-public/testing (#2876)

We should use the same images in the testing BK org as in the prod BK
orgs.

buildkite/bazelci.py

diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index deb7a2b..52e263e 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -327,11 +327,6 @@
     "bazel": DOWNSTREAM_PROJECTS_PRODUCTION,
 }[BUILDKITE_ORG]
 
-DOCKER_REGISTRY_PREFIX = {
-    "bazel-testing": "bazel-public/testing",
-    "bazel-trusted": "bazel-public",
-    "bazel": "bazel-public",
-}[BUILDKITE_ORG]
 
 # Platforms we no longer support, but still exist in the artifact registry.
 # NOTE: These names are the ones use din the PLATFORMS dict, not the
@@ -427,8 +422,6 @@
 
 
 def get_docker_image(image_name, is_arm64=False):
-    if THIS_IS_TESTING:
-        return f"gcr.io/{DOCKER_REGISTRY_PREFIX}/{image_name}"
     digests = IMAGE_HASHES.get(image_name)
     if not digests:
         raise ValueError(f"No digest found for docker image: {image_name}")
@@ -436,7 +429,7 @@
     digest = digests.get(arch)
     if not digest:
         raise ValueError(f"No {arch} digest found for docker image: {image_name}")
-    return f"gcr.io/{DOCKER_REGISTRY_PREFIX}/{image_name}@{digest}"
+    return f"gcr.io/bazel-public/{image_name}@{digest}"
 
 
 # A map containing all supported platform names as keys, with the values being

buildkite/docker/build.sh

diff --git a/buildkite/docker/build.sh b/buildkite/docker/build.sh
index 2c21416..62f1bf6 100755
--- a/buildkite/docker/build.sh
+++ b/buildkite/docker/build.sh
@@ -2,17 +2,7 @@
 
 set -euxo pipefail
 
-case $(git symbolic-ref --short HEAD) in
-    master)
-        PREFIX="bazel-public"
-        ;;
-    testing)
-        PREFIX="bazel-public/testing"
-        ;;
-    *)
-        echo "You must build Docker images either from the master or the testing branch!"
-        exit 1
-esac
+PREFIX=bazel-public
 
 # Enable use of buildkit for all builds. No extra support in the Dockerfile is required.
 # See https://docs.docker.com/develop/develop-images/build_enhancements/ for details.

buildkite/docker/push.sh

diff --git a/buildkite/docker/push.sh b/buildkite/docker/push.sh
index 323b725..8ccff49 100755
--- a/buildkite/docker/push.sh
+++ b/buildkite/docker/push.sh
@@ -1,18 +1,7 @@
 #!/bin/bash
 
 set -euxo pipefail
-
-case $(git symbolic-ref --short HEAD) in
-    master)
-        PREFIX="bazel-public"
-        ;;
-    testing)
-        PREFIX="bazel-public/testing"
-        ;;
-    *)
-        echo "You must build Docker images either from the master or the testing branch!"
-        exit 1
-esac
+PREFIX=bazel-public
 
 # Containers used by Bazel CI
 docker push "gcr.io/$PREFIX/rockylinux8" &