Stop tagging releases as prereleases (#3259)

## Motivation and Context
Now that we have started [stable
releases](https://github.com/smithy-lang/smithy-rs/releases) since
`release-2023-11-21`, we shouldn't set those as pre-releases.

(this PR also includes a small fix to the `Release` job in our release
workflow to avoid `git push` failing during dry-runs, which [a previous
dry-run](https://github.com/smithy-lang/smithy-rs/actions/runs/6989359794)
ran into)

## Description
The fix is in `changelogger`, and this should remove pre-releases from
releases in `smithy-rs` as well as those in `aws-sdk-rust`.

## Testing
Ran a
[dry-run](https://github.com/smithy-lang/smithy-rs/actions/runs/7007835035)
and checked the release artifacts as follows:
```
{
  "tagName": "release-2023-11-27",
  "name": "November 27th, 2023",
  "body": "",
  "prerelease": false
}
```

Have not verified what a release manifest looks like in `aws-sdk-rust`,
but I suspect `prerelease: false` should be applied there as well given
the same `changelogger` is used.

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