ci: update

Author: sfan5

.github/workflows/build.yml

@@ -10,15 +10,15 @@ jobs:
   webpage:
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Checkout build sources
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           repository: mpv-player/mpv.io
 
       - name: Checkout build result repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           repository: mpv-player/mpv-player.github.io
           ref: master
@@ -33,7 +33,6 @@ jobs:
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:
-          ruby-version: "2.1"
           bundler-cache: true # runs 'bundle install' and caches installed gems automatically
 
       - name: Build site and manual