[CI] Potential fix for code scanning alert no. 2150: Workflow does not contain permissions (#13230)

Potential fix for code scanning alert no. 2150: Workflow does not contain permissions

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

Author: 3 people

.github/workflows/pr_tests_gpu.yml

@@ -1,5 +1,8 @@
 name: Fast GPU Tests on PR
 
+permissions:
+  contents: read
+
 on:
   pull_request:
     branches: main