Fix maturin build path issue

The previous change broke the build by looking for Cargo.toml in the wrong directory.
Reverted to running maturin from polars-bio-bench with explicit -m ../Cargo.toml path.

This maintains the cargo cache improvements while fixing the build error.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: mwiewior

.github/workflows/benchmark.yml

@@ -217,9 +217,8 @@ jobs:
           # Install maturin in poetry virtualenv
           cd polars-bio-bench
           poetry run pip install maturin
-          # Build from repo root to ensure proper cache usage
-          cd ..
-          poetry run -C polars-bio-bench maturin develop --release
+          # Build from repo root with explicit Cargo.toml path
+          poetry run maturin develop --release -m ../Cargo.toml
 
       - name: Run target benchmarks
         run: |