remove unused function

src/rougail/utils.py

@@ -5,11 +5,6 @@ from unicodedata import normalize, combining
 from .i18n import _
 
 
-def valid_name(name: str) -> None:
-    if '.' in name:
-        raise ValueError(_(f'"{name}" is a forbidden variable or family name, dot is not allowed'))
-
-
 def normalize_family(family_name: str) -> str:
     """replace space, accent, uppercase, ... by valid character
     """