[Test] Disable a failing test on Windows.

Author: hborla

test/IRGen/async/run-partialapply-capture-generic_conformer-and-generic-to-void.sil

@@ -12,6 +12,9 @@
 // REQUIRES: concurrency
 // UNSUPPORTED: use_os_stdlib
 
+// This test is failing on Windows.
+// UNSUPPORTED: OS=windows-msvc
+
 import Builtin
 import Swift
 import _Concurrency