gh-133346: make _colorize.Argparse kw-only constructible (GH-140620)

Other themes are kw-only constructible.
(cherry picked from commit 387ac2d)

Co-authored-by: Bénédikt Tran <[email protected]>

Author: picnixz

Lib/_colorize.py

@@ -155,7 +155,7 @@ def __iter__(self) -> Iterator[str]:
         return iter(self.__dataclass_fields__)
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, kw_only=True)
 class Argparse(ThemeSection):
     usage: str = ANSIColors.BOLD_BLUE
     prog: str = ANSIColors.BOLD_MAGENTA