Issue #22064: Improve the misleading message from 2to3 when skipping optional fixers.

Patch by Vinod Kurup.
diff --git a/Lib/lib2to3/refactor.py b/Lib/lib2to3/refactor.py
index c24be14..adf9996 100644
--- a/Lib/lib2to3/refactor.py
+++ b/Lib/lib2to3/refactor.py
@@ -255,7 +255,7 @@
             fixer = fix_class(self.options, self.fixer_log)
             if fixer.explicit and self.explicit is not True and \
                     fix_mod_path not in self.explicit:
-                self.log_message("Skipping implicit fixer: %s", fix_name)
+                self.log_message("Skipping optional fixer: %s", fix_name)
                 continue
 
             self.log_debug("Adding transformation: %s", fix_name)