ci(torch xla): use JETSTREAM_PT_DISABLE env var in command line

For some reason the env var was not carried on (though Jetstream was
disabled anyway). Moving the variable to the command line invocation
will remove a warning in the logs.

.github/workflows/test-pytorch-xla-tpu.yml

@@ -25,11 +25,10 @@ jobs:
     env:
       PJRT_DEVICE: TPU
       HF_HUB_CACHE: /mnt/hf_cache/cache_huggingface
-      JETSTREAM_PT_DISABLE: 1 # Disable Jetstream Pytorch tests
     steps:
       - name: Checkout
         uses: actions/checkout@v4
 
       - name: Build and test optimum tpu
         run: |
-          HF_TOKEN=${{ secrets.HF_TOKEN_OPTIMUM_TPU_CI }} make tests
+          JETSTREAM_PT_DISABLE=1 HF_TOKEN=${{ secrets.HF_TOKEN_OPTIMUM_TPU_CI }} make tests