chore: use correct prettier version in ci (#8321)

Install prettier in package.json + yarn.lock. Global install was using incorrect version

.github/workflows/ci.yaml

@@ -203,7 +203,16 @@ jobs:
           go-version: 1.20.5
 
       - name: Install prettier
-        run: npm install -g prettier
+        # We only need prettier for fmt, so do not install all dependencies.
+        # There is no way to install a single package with yarn, so we have to
+        # make a new package.json with only prettier listed as a dependency.
+        # Then running `yarn` will only install prettier.
+        run: |
+          cd site
+          mv package.json package.json.bak
+          jq '{dependencies: {prettier: .devDependencies.prettier}}' < package.json.bak > package.json
+          yarn --frozen-lockfile
+          mv package.json.bak package.json
 
       - name: Install shfmt
         run: go install mvdan.cc/sh/v3/cmd/shfmt@v3.5.0