Update gh-pages.yml

Author: jmid

.github/workflows/gh-pages.yml

@@ -10,11 +10,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Cache opam
         id: cache-opam
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: ~/.opam
           key: opam-ubuntu-latest-5.0.0