Sync typeshed (#5981)

gvanrossum · web-flow · commit 18d43250333c · 2018-11-30T13:29:42.000-08:00
To incorporate python/typeshed#2658
diff --git a/mypy/typeshed b/mypy/typeshed
@@ -1 +1 @@
-Subproject commit eaeb5fcf13034135efd487303c1dd8ed00348950
+Subproject commit de50614957f3f599a6abe403d5508e9c53f8ad21
