normalize gitconfig's author field to UTF-8 NFC

Fixes python-poetry#8779

src/poetry/console/commands/init.py

@@ -458,8 +458,9 @@ def _format_requirements(self, requirements: list[dict[str, str]]) -> Requiremen
 
     def _validate_author(self, author: str, default: str) -> str | None:
         from poetry.core.packages.package import AUTHOR_REGEX
+        from poetry.core.utils.helpers import combine_unicode
 
-        author = author or default
+        author = combine_unicode(author or default)
 
         if author in ["n", "no"]:
             return None