Fix run-readme-pr-mps syntax (#792)

By deleting the tab

Test plan: https://github.com/pytorch/torchchat/actions/runs/9071559070?pr=792 (i.e. workflow is running as it is syntactically correct now)

Author: malfet

.github/workflows/run-readme-pr-mps.yml

@@ -43,7 +43,7 @@ jobs:
           echo "*******************************************"
           bash -x ./run-readme.sh
           echo "::endgroup::"
-
+  
   test-quantization-mps-macos:
     uses: pytorch/test-infra/.github/workflows/macos_job.yml@main
     with: