chore(deps): pin actions/checkout action to 50fbc62

GitOrigin-RevId: 4254c13ea494ec872c325741a40a594a04e7cb8a
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d63e8c4..a7a0c36 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -14,7 +14,7 @@
     runs-on: ubuntu-latest
     steps:
       - name: Checkout master
-        uses: actions/checkout@v1
+        uses: actions/checkout@50fbc622fc4ef5163becd7fab6573eac35f8462e # v1
 
       - name: Deploy docs
         uses: mhausenblas/mkdocs-deploy-gh-pages@master