Rename codename_override to codename

Match the Cloudsmith setup script's native environment variable
name. The script accepts codename=<value> to override OS
detection without patching /etc/os-release.

Author: bschwedler

package-manager/template/Containerfile.ubuntu2604.jinja2

@@ -28,7 +28,7 @@ ENV STARTUP_DEBUG_MODE=0
 SHELL ["/bin/bash", "-euo", "pipefail", "-c"]
 
 ### Setup environment ###
-{{ apt.run_setup(codename_override="noble") }}
+{{ apt.run_setup(codename="noble") }}
 
 ### Install Apt Packages ###
 COPY {{ Path.Version }}/deps/ubuntu-26.04_packages.txt /tmp/packages.txt