Grant "write" permission to "github-actions[bot]" (#621)

Summary:
Pull Request resolved: #621

Grant "write" permission to "github-actions[bot]" to avoid permission issue in deploying github page (https://github.com/pytorch/opacus/actions/runs/7659084329).

Reviewed By: karthikprasad

Differential Revision: D53131111

fbshipit-source-id: 86e722035c2a0bb9e69721953791b9206f45ad26

.github/workflows/deploy.yml

@@ -9,6 +9,9 @@ jobs:
   deploy:
     name: Deploy to GitHub Pages
     runs-on: ubuntu-latest
+    permissions:
+      # Grant write permission here so it can be pushed to gh-pages branch
+      contents: write
     defaults:
       run:
         working-directory: website