ci: drop placeholder for rust and clang due to long downloads
What does this MR do and why?
ci: drop placeholder for rust and clang due to long downloads
Seems like these jobs don't keep the caches around, so the runtime takes
longer on them. Keep only the sanity job.
Partly reverts: 87b9c09264e8 ("ci: tag sanity, rustfmt and clang-format job as a "placeholder" job")
Signed-off-by: David Heidelberg <david.heidelberg@collabora.com>
/cc @daniels