Update UnitTests.yml

Explicit, list runner

Author: coolkp

.github/workflows/UnitTests.yml

@@ -33,7 +33,7 @@ jobs:
       matrix:
         tpu-type: ["v5-8"]
     name: "TPU test (${{ matrix.tpu-type }})"
-    runs-on: ["self-hosted", "tpu", "${{ matrix.tpu-type }}"]
+    runs-on: ["self-hosted", "tpu", "${{ matrix.tpu-type }}","maxdiffusion-github-runner-2"]
     steps:
     - uses: actions/checkout@v4
     - name: Set up Python 3.12