PasswordProcessor: Fix typo in docstring

Author: plotski

prompt_toolkit/layout/processors.py

@@ -314,7 +314,7 @@ def apply_transformation(
 
 class PasswordProcessor(Processor):
     """
-    Processor that turns masks the input. (For passwords.)
+    Processor that masks the input. (For passwords.)
 
     :param char: (string) Character to be used. "*" by default.
     """