style(template): remove auto-generated headers from version stub

Remove the "@generated" and "DO NOT EDIT" header comments from the `_version.pyi` template. This simplifies the generated file without changing its functional interface.

Author: liblaf

template/src/{{ package_dir }}/_version.pyi

@@ -1,6 +1,3 @@
-# This file is @generated by <https://github.com/liblaf/copier-python>.
-# DO NOT EDIT!
-
 # ref: <https://github.com/ofek/hatch-vcs>
 # ref: <https://github.com/pypa/setuptools-scm/blob/58ed7d5dec0e3bc80190f73543cf4d8a6876ba8e/src/setuptools_scm/_integration/dump_version.py#L16-L51>
 __commit_id__: str | None