mypy: turn off warn for unused ignore in --py3

Author: manu-chroma

Makefile

@@ -178,7 +178,7 @@ mypy3: ${PYSOURCES}
 	ln -s $(shell python -c 'from __future__ import print_function; import ruamel.yaml; import os.path; print(os.path.dirname(ruamel.yaml.__file__))') \
 		typeshed/2and3/ruamel/
 	MYPYPATH=$MYPYPATH:typeshed/3:typeshed/2and3 mypy --disallow-untyped-calls \
-		 --warn-redundant-casts --warn-unused-ignores \
+		 --warn-redundant-casts \
 		 schema_salad
 
 jenkins: