Don’t warn for unused ignores (matplotlib#15043)

Author: alexrudy

doc/conf.py

@@ -106,6 +106,7 @@ def _check_dependencies():
 nitpicky = True
 # change this to True to update the allowed failures
 missing_references_write_json = False
+missing_references_warn_unused_ignores = False
 
 intersphinx_mapping = {
     'python': ('https://docs.python.org/3', None),