Match RELEASE_TAG on preview to tag correctly. (#31)

## Motivation

<!-- Why are you making this change, what problem does it solve? Include links to relevant tickets. -->

https://github.com/DataDog/openfeature-js-client/actions/runs/17501446809/job/49715076852

```
npm notice Tarball Details
npm notice name: @datadog/flagging-core
npm notice version: 0.1.0-preview.2
npm notice filename: datadog-flagging-core-0.1.0-preview.2.tgz
npm notice package size: 3.6 kB
npm notice unpacked size: 16.4 kB
npm notice shasum: 7618508441404f4061502e5ffbeb6c4b59835d2e
npm notice integrity: sha512-V/44f/RDNruoY[...]hzNN0I90lR5mg==
npm notice total files: 33
npm notice
npm notice Publishing to https://registry.npmjs.org/ with tag alpha and public access
+ @datadog/flagging-core@0.1.0-preview.2
```

The build with github tag `preview.2` was pushed as `alpha` on npm.

## Changes

<!-- What does this change exactly? Who will be affected? Include relevant screenshots, videos, links. Please highlight all the changes that you are not sure about (ex: AI agent generated) -->

Remove qoutes.

## Test instructions

<!-- How can the reviewer test this change? Include relevant steps to reproduce the issue, if any. -->

<img width="786" height="687" alt="Screenshot 2025-09-05 at 2 38 19 PM" src="https://github.com/user-attachments/assets/a1481033-555e-4b5b-a9b3-5bb33fb9e752" />

## Checklist

<!-- By submitting this test, you confirm the following: -->

- [ ] Updated Documentation
- [ ] Tested locally
- [ ] Tested on staging
- [ ] Added unit tests for this change.
- [ ] Added e2e/integration tests for this change.

<!-- Also, please read the contribution guidelines: https://github.com/DataDog/openfeature-js-client/blob/main/CONTRIBUTING.md -->

Author: leoromanovsky

.github/workflows/prerelease.yaml

@@ -61,7 +61,7 @@ jobs:
           RELEASE_TAG="${{ github.event.release.tag_name }}"
           
           # Check if the release tag contains "preview"
-          if [[ "$RELEASE_TAG" =~ '.*preview.*' ]]; then
+          if [[ "$RELEASE_TAG" =~ .*preview.* ]]; then
             echo "tag=preview" >> "$GITHUB_OUTPUT"
             echo "Using 'preview' npm tag for release $RELEASE_TAG"
           else