[workflow] Switch back to manual rustup invocation

The actions-rs workflow appears to be unmaintained.  We can still install
minimal Rust toolchain components with rustup.

Author: mshroyer

.github/workflows/ci.yml

@@ -32,11 +32,9 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Setup rust
-        uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: ${{ matrix.toolchain }}
-          components: rustfmt, clippy
+        run: |
+          rustup toolchain install --profile minimal -c rustfmt,clippy ${{ matrix.toolchain }} && \
+          rustup default ${{ matrix.toolchain }}
 
       - name: Install uv
         uses: astral-sh/setup-uv@v5