ci(release-rpm): drop apt awscli, use runner's pre-installed AWS CLI v2 (2.3)

[fcostaoliveira]

Summary

Backport of #368 to the 2.3 release branch.

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

```
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). GitHub's ubuntu-latest now resolves to noble. The ubuntu-24.04 runner image ships AWS CLI v2 pre-installed at /usr/local/bin/aws, so the apt install was both redundant and broken.

This PR drops awscli from the apt list and adds aws --version as a sanity check on 2.3, so 2.3.x patch releases keep publishing to YUM.

Once this lands we can re-trigger publish-to-yum against the 2.3.1 release via workflow_dispatch to backfill the YUM repo with the 2.3.1 RPMs (which already exist as release assets but are not yet served from the repo).

🤖 Generated with Claude Code

---

Note

Low Risk
Low risk workflow tweak that only affects the publish-to-yum GitHub Actions job by changing how AWS CLI is obtained; main risk is unexpected runner image differences causing publish failures.

Overview
Fixes the RPM release workflow on Ubuntu 24.04 runners by dropping awscli from the apt install in publish-to-yum and instead relying on the GitHub-hosted runner’s pre-installed AWS CLI v2.

Adds an aws --version sanity check while still installing only the required RPM repo tooling (createrepo-c, rpm).

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