chore: use rust cache in docs workflow

.github/workflows/docs-pr.yml

@@ -53,6 +53,14 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
+
+      - name: Setup toolchain
+        uses: dtolnay/[email protected]
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          key: x86_64-unknown-linux-gnu
+          save-if: false
 
       - name: Install Yarn dependencies
         uses: ./.github/actions/setup