Disable Y026 from flake8-pyi (#6958)

Dependent on PyCQA/flake8-pyi#101.

.flake8

@@ -17,10 +17,13 @@
 #       F403 import *' used; unable to detect undefined names
 #       F405 defined from star imports
 
+# Rules that we'd like to enable in the future:
+#       Y026 Use typing_extensions.TypeAlias for type aliases (blocked by #4913)
+
 [flake8]
 per-file-ignores =
   *.py: E203, E501
-  *.pyi: E301, E302, E305, E501, E701, E741, F401, F403, F405, F822
+  *.pyi: E301, E302, E305, E501, E701, E741, F401, F403, F405, F822, Y026
   # Since typing.pyi defines "overload" this is not recognized by flake8 as typing.overload.
   # Unfortunately, flake8 does not allow to "noqa" just a specific error inside the file itself.
   # https://github.com/PyCQA/flake8/issues/1079