ci: update

Author: sfan5

Diff for: .github/workflows/build.yml

@@ -8,17 +8,17 @@ on:
 
 jobs:
   webpage:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Checkout build sources
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: mpv-player/mpv.io
 
       - name: Checkout build result repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: mpv-player/mpv-player.github.io
           ref: master