Enforce keyword-only arguments in make_image_file (#2989)

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: adamtheturtle

tests/mock_vws/utils/__init__.py

@@ -85,6 +85,7 @@ def auth_header_content_type(self) -> str:
 
 @beartype
 def make_image_file(
+    *,
     file_format: str,
     color_space: Literal["RGB", "CMYK"],
     width: int,