ci: Replace rustup update with external installation action

rust-lang/rustup#3409 (comment)

.github/workflows/rustapi.yml

@@ -21,9 +21,7 @@ jobs:
       - name: Prepare virtual environment
         run: |
           pip install .
-      - name: Install Rust
-        run: |
-          rustup update
+      - uses: dtolnay/rust-toolchain@stable
       - name: Check and lint
         working-directory: crate
         run: |