fix(ci): install pnpm in release workflow to unblock tests (#435)

## Description

> Describe what you did and why.

**Related issue (if any):** fixes #issue_number_goes_here

## Checklist

- [x] I have followed this repository's contributing guidelines.
- [x] I will adhere to the project's code of conduct.

## Additional information

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Author: a-oren

.github/workflows/release.yml

@@ -91,6 +91,9 @@ jobs:
           echo "Maven artifact exists: ${{ steps.check_maven.outputs.maven_exists }}"
           echo "Will publish to Maven Central: ${{ steps.check_maven.outputs.maven_exists == 'false' }}"
 
+      - name: Install pnpm
+        run: pnpm install -g pnpm
+
       - name: Compute Maven profiles
         id: compute_profiles
         run: |