Remove avoid_private_typedef_functions from recommend.yaml (#2517)

As discussed in our meeting today.

Author: goderbauer

tool/canonical/recommend.yaml

@@ -5,7 +5,6 @@ linter:
     - avoid_function_literals_in_foreach_calls
     - avoid_init_to_null
     - avoid_null_checks_in_equality_operators
-    - avoid_private_typedef_functions
     - avoid_renaming_method_parameters
     - avoid_return_types_on_setters
     - avoid_returning_null_for_void