Extend timeout for run-readme-pr-mps.yml

Readme run on M1 with MPS takes over 30 minutes, and may be hitting default timeout.  Extending timeout.

Author: mikekgfb

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

@@ -10,6 +10,7 @@ jobs:
     uses: pytorch/test-infra/.github/workflows/macos_job.yml@main
     with:
       runner: macos-m1-14
+      timeout-minutes: 50
       script: |
           conda create -y -n test-readme-mps-macos python=3.10.11 llvm-openmp
           conda activate test-readme-mps-macos