lock: do not attempt to walk up when computing relative paths

This option of relative_to appeared in Python 3.12.
I estimate supporting this is not worth the additional complexity
at the moment.

Author: sbidoul

src/pip/_internal/models/pylock.py

@@ -105,7 +105,7 @@ def from_install_requirement(cls, ireq: InstallRequirement, base_dir: Path) -> S
                 package.directory = PackageDirectory(
                     path=(
                         Path(url_to_path(download_info.url))
-                        .relative_to(base_dir, walk_up=True)
+                        .relative_to(base_dir)
                         .as_posix()
                     ),
                     editable=(