chore: exclude lance-graph-python in build (#152)

This PR excludes the `lance-graph-python` package in the `cargo build`,
since it needs to be built by maturin. The issue would cause build
errors in the MacOS.

A similar fix has also been applied in the `lance` project
https://github.com/lance-format/lance/blob/main/Cargo.toml#L25

Author: ChunxuTang

Cargo.lock

@@ -2,7 +2,8 @@
 members = [
     "crates/lance-graph",
     "crates/lance-graph-catalog",
-    "crates/lance-graph-python",
     "crates/lance-graph-benches",
 ]
+# Python package needs to be built by maturin.
+exclude = ["crates/lance-graph-python"]
 resolver = "2"