Introduce container_registry for image prefix

Change-Id: I80067f53aa2b63286b654fff782f0f7b65a2d050
diff --git a/images/heat/Dockerfile b/images/heat/Dockerfile
index 94b5e2b..6d37b52 100644
--- a/images/heat/Dockerfile
+++ b/images/heat/Dockerfile
@@ -1,9 +1,10 @@
 # SPDX-License-Identifier: Apache-2.0
 # Atmosphere-Rebuild-Time: 2024-06-25T22:49:25Z
 
+ARG REGISTRY
 ARG RELEASE
 
-FROM harbor.atmosphere.dev/library/openstack-venv-builder:${RELEASE} AS build
+FROM ${REGISTRY}/openstack-venv-builder:${RELEASE} AS build
 ARG HEAT_GIT_REF=80eea85194825773d1b60ecc4386b2d5ba52a066
 ADD --keep-git-dir=true https://opendev.org/openstack/heat.git#${HEAT_GIT_REF} /src/heat
 RUN git -C /src/heat fetch --unshallow
@@ -13,7 +14,7 @@
         /src/heat
 EOF
 
-FROM harbor.atmosphere.dev/library/openstack-python-runtime:${RELEASE}
+FROM ${REGISTRY}/openstack-python-runtime:${RELEASE}
 RUN <<EOF bash -xe
 apt-get update -qq
 apt-get install -qq -y --no-install-recommends \