chore: update example code in CONTRIBUTING.md

Author: Ben Rowland

.github/CONTRIBUTING.md

@@ -189,7 +189,9 @@ usable as:
 ```python
 from scikit_build_core.settings.skbuild_settings import SettingsReader
 
-settings_reader = SettingsReader(Path("pyproject.toml"), config_settings or {})
+settings_reader = SettingsReader.from_file(
+    Path("pyproject.toml"), config_settings or {}
+)
 setting = settings_reader.settings
 assert settings.cmake.minimum_version == "3.15"
 assert settings.ninja.minimum_version == "1.5"