update to PyO3 0.21.1, bump version to 2.18 (#1261)

Author: davidhewitt

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "pydantic-core"
-version = "2.17.0"
+version = "2.18.0"
 edition = "2021"
 license = "MIT"
 homepage = "https://github.com/pydantic/pydantic-core"
@@ -27,7 +27,7 @@ include = [
 rust-version = "1.76"
 
 [dependencies]
-pyo3 = { version = "0.21.0", features = ["generate-import-lib", "num-bigint"] }
+pyo3 = { version = "0.21.1", features = ["generate-import-lib", "num-bigint"] }
 regex = "1.10.3"
 strum = { version = "0.25.0", features = ["derive"] }
 strum_macros = "0.26.1"