tests: disable IRGen/nested_generics.swift for arm64e

The check lines don't consider ptrauth

rdar://131554269

Author: eeckstein

test/IRGen/nested_generics.swift

@@ -10,6 +10,7 @@
 // rdar://131554269
 //
 // REQUIRES: optimized_stdlib
+// UNSUPPORTED: CPU=arm64e
 
 func blah<T>(_: T.Type) {}