docker: bump atc0005/go-ci in /dependabot/docker/builds

Bumps [atc0005/go-ci](https://github.com/atc0005/go-ci) from go-ci-unstable-build-v0.13.7 to go-ci-unstable-build-v0.13.8.
- [Release notes](https://github.com/atc0005/go-ci/releases)
- [Changelog](https://github.com/atc0005/go-ci/blob/master/CHANGELOG.md)
- [Commits](https://github.com/atc0005/go-ci/commits)

---
updated-dependencies:
- dependency-name: atc0005/go-ci
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

dependabot/docker/builds/Dockerfile

@@ -13,7 +13,7 @@
 
 # https://github.com/atc0005/go-ci/releases
 # https://github.com/atc0005/go-ci/pkgs/container/go-ci
-FROM ghcr.io/atc0005/go-ci:go-ci-unstable-build-v0.13.7
+FROM ghcr.io/atc0005/go-ci:go-ci-unstable-build-v0.13.8
 
 # Setup isolated build environment with a full copy of the Git repo contents
 # MINUS any file or path listed in the .dockerignore file at the root of this