ci : use ubuntu-latest for gguf-publish workflow (#19951)
This commit changes the runner for the gguf-publish workflow from
ubuntu-slim back to ubuntu-latest, which was updated in Commit
142cbe2ac68978e5dec3a2e19c1b64ef1c5740b1 ("ci : use new 1vCPU runner for
lightweight jobs (#19107)").
The motivation for this is that the action used in the workflow depends
on the docker daemon, which does not seem not available in the
ubuntu-slim runner. This is currently causing an error in the workflow
and preventing the gguf-publish workflow from running successfully.
Today was the the first time since the original change (I think) that
publish task has been run which may be why the issue was not noticed
before.
Refs: https://github.com/ggml-org/llama.cpp/actions/runs/22481900566
