Update external/mypy to 0.790

KKawamura1 · KKawamura1 · commit cd608f40ab6b · 2020-10-15T13:56:36.000+09:00
diff --git a/external/mypy b/external/mypy
@@ -1 +1 @@
-Subproject commit d9dea5f3ad30bb449e4167b3e8476684ded0482e
+Subproject commit 69a055a7632e2444fcb2bfb022d04f4546358d50
