Update generate.yml

- update runs-on to ubuntu-22.04
- update to actions/checkout@v4

Author: yoshisatoyanagisawa

.github/workflows/generate.yml

@@ -7,9 +7,9 @@ on:
 jobs:
   main:
     name: Build, Validate and Deploy Locally
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: w3c/spec-prod@v2
         with:
           GH_PAGES_BRANCH: gh-pages