ci(release-rpm): drop apt awscli, use runner's pre-installed AWS CLI v2

[fcostaoliveira]

Summary

The 2.3.1 release's publish-to-yum job failed in step 4 with:

```
Package awscli is not available, but is referred to by another package.
E: Package 'awscli' has no installation candidate
```

Failed run: https://github.com/redis/memtier_benchmark/actions/runs/25385139928/job/74444847195

Ubuntu dropped the awscli apt package in 24.04 (noble) — the v1 it shipped was years out of date. GitHub Actions' `ubuntu-latest` now resolves to noble, so the apt install can never satisfy awscli again.

The fix is straightforward: GitHub's ubuntu-24.04 runner image ships AWS CLI v2 pre-installed at /usr/local/bin/aws, so the apt install line was both redundant and broken. Drop awscli from the apt list, add aws --version as a sanity check.

Effect on the 2.3.1 release

The release tag, RPMs (build + smoke test) and Docker images all completed successfully — publish-to-yum is the last step that copies signed RPMs into the public S3-backed YUM repo. The 2.3.1 RPMs exist as release assets but are not yet served from the YUM repo. Once this lands, we can re-trigger publish-to-yum against the 2.3.1 release via workflow_dispatch (or by transient unpublish/republish) to backfill the repo.

Where this also needs to land

Same fix is needed on the 2.3 branch so 2.3.x patch releases keep publishing. I'll open a sibling PR after this one lands, or feel free to cherry-pick directly.

🤖 Generated with Claude Code

---

Note

Low Risk
Low risk: workflow-only change that adjusts package installation for the GitHub runner image; main risk is if the runner image no longer includes aws or its path/version differs, breaking the publish job.

Overview
Fixes publish-to-yum in release-rpm.yml on ubuntu-latest (now Ubuntu 24.04) by removing awscli from the apt install and installing only RPM tooling (createrepo-c, rpm).

Adds a small sanity check (aws --version) and clarifying comments to ensure the runner’s preinstalled AWS CLI v2 is available before syncing the YUM repo to S3.

^{Reviewed by Cursor Bugbot for commit 11e2a53. Bugbot is set up for automated code reviews on this repo. Configure here.}