Explicitly install Rust toolchain in GitHub test action

.github/workflows/test.yml

@@ -13,6 +13,15 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
-    - name: Run tests
-      run: cargo test --verbose
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+          components: rust-src
+
+      - name: Run tests
+        run: cargo test --verbose