Update mypy/main.py: the only write without a newline...

Author: wyattscarpenter

mypy/main.py

@@ -411,7 +411,7 @@ def _print_message(self, message: str, file: SupportsWrite[str] | None = None) -
         if message:
             if file is None:
                 file = self.stderr
-            print(message, file=file)
+            print(message, file=file, end='')
 
     # ===============
     # Exiting methods