Pin CUDA nightlies for mx failures (pytorch#428)

* Pin CUDA nightlies for mx failures

* Update regression_test.yml

* Update regression_test.yml

Author: msaroufim

.github/workflows/regression_test.yml

@@ -33,7 +33,7 @@ jobs:
             gpu-arch-version: "12.1"
           - name: CUDA Nightly
             runs-on: linux.g5.12xlarge.nvidia.gpu
-            torch-spec: '--pre torch --index-url https://download.pytorch.org/whl/nightly/cu121'
+            torch-spec: '--pre torch==2.5.0.dev20240620+cu121 --index-url https://download.pytorch.org/whl/nightly/cu121'
             gpu-arch-type: "cuda"
             gpu-arch-version: "12.1"
           - name: CPU 2.2.2