CI: Unity tests use serial/license again (restore UNITY_LICENSE)

Author: dsarno

.github/workflows/unity-tests.yml

@@ -45,6 +45,7 @@ jobs:
         env:
           UNITY_EMAIL: ${{ secrets.UNITY_EMAIL }}
           UNITY_PASSWORD: ${{ secrets.UNITY_PASSWORD }}
+          UNITY_LICENSE: ${{ secrets.UNITY_LICENSE }}
         with:
           projectPath: ${{ matrix.projectPath }}
           unityVersion: ${{ matrix.unityVersion }}