Update caddy-docker-proxy version to v2.13.1

[github-actions]

Update caddy-docker-proxy from upstream

Update Dockerfile ARG CDP_VERSION

changed lines [5 14] of file "rootfs/Dockerfile"

v2.13.1

## What's Changed
* fix: don't warn "not in same network" for stopped containers without an IP by @lucaslorentz in https://github.com/lucaslorentz/caddy-docker-proxy/pull/822
* fix: enable the admin API by default again, disable via CADDY_ADMIN=off by @lucaslorentz in https://github.com/lucaslorentz/caddy-docker-proxy/pull/823


**Full Changelog**: https://github.com/lucaslorentz/caddy-docker-proxy/compare/v2.13.0...v2.13.1

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