[lldb] Disable TestSwiftStepInAsync.py

This is blocking PR testing, disable until we can take a better look.

rdar://116529018

Author: bulbazord

lldb/test/API/lang/swift/async/stepping/step-in/TestSwiftStepInAsync.py

@@ -10,6 +10,7 @@ class TestCase(lldbtest.TestBase):
 
     @swiftTest
     @skipIf(oslist=['windows', 'linux'])
+    @skipIf(bugnumber="rdar://116529018")
     def test(self):
         """Test step-in to async functions"""
         self.build()