Fix release workflow authentication for create_release

[Copilot]

The create_release GitHub Actions job was failing during release creation with Bad credentials. This updates the release workflow to use the repository-scoped Actions token for same-repo release operations instead of the custom admin token.

• Release job authentication

  • Switched create_release to use ${{ github.token }} for:
    • release creation
    • release asset uploads
  • Leaves ADMIN_GEOPORTAL_TOKEN in place for cross-repo operations (geoportal-access-lib-samples), where elevated/repository-external access is still required

• Scope of change

  • Restricted to .github/workflows/release.yml
  • No changes to build, publish, or artifact generation logic

• Example

  - name: Create Release
    uses: actions/create-release@v1.1.2
    env:
      GITHUB_TOKEN: ${{ github.token }}