fix: change NUGET_API_KEY -> NUGET_TOKEN (#67)

Author: benjiro

.github/workflows/release.yml

@@ -40,5 +40,5 @@ jobs:
         if: ${{ steps.release.outputs.releases_created }}
         run: |
           dotnet nuget push OpenFeature.${{ steps.release.outputs.major }}.${{ steps.release.outputs.minor }}.${{ steps.release.outputs.patch }}.nupkg `
-            --api-key ${{secrets.NUGET_API_KEY}} `
+            --api-key ${{secrets.NUGET_TOKEN}} `
             --source https://api.nuget.org/v3/index.json