Downgrade the `download-artifact` and `upload-artifact` actions to v3 due to...

Downgrade the `download-artifact` and `upload-artifact` actions to v3 due to breaking changes. (#16847)

Partially reverts #16796

This is causing errors of the form:

```
Error: Failed to CreateArtifact: Received non-retryable error: Failed request: (409) Conflict: an artifact with this name already exists on the workflow run
```

for the debs and wheels stages.


There were breaking changes that weren't included in the dependabot
changelog (:/):
https://github.com/actions/upload-artifact#breaking-changes




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Base: `release-v1.100` <!-- git-stack-base-branch:release-v1.100 -->

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Original commit schedule, with full messages:

<ol>
<li>

Downgrade the `upload-artifact` and `download-artifact` actions to v3 

</li>
</ol>

---------

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>