Add REQUIRES: distributed to runtime_discoverable_attrs_distributed.swift (#63669)

The test is using the distributed capabilities, but it is not marked as
such. If someone is not building with the distributed features enabled,
the test will fail for them.

Author: drodriguez

test/type/runtime_discoverable_attrs_distributed.swift

@@ -3,6 +3,7 @@
 // RUN: %target-typecheck-verify-swift -disable-availability-checking -enable-experimental-feature RuntimeDiscoverableAttrs -I %t
 
 // REQUIRES: asserts
+// REQUIRES: distributed
 
 import RuntimeAttrs
 import Distributed