[Tests] Fix introspection failing due to a typo. (#7377)

Fixes: https://github.com/xamarin/maccore/issues/2052

tests/introspection/ApiTypoTest.cs

@@ -180,6 +180,7 @@ namespace Introspection
 			"Descendents",
 			"Descrete",
 			"Dhe", // Diffie–Hellman key exchange
+			"Diffable", // that you can diff it.. made up word from apple
 			"Differental",
 			"Diffie",
 			"Directionfor",