Concurrency: correct symbol storage annotation

This marks the decls as being defined in swift_Concurrency rather than
swiftCore.  This corrects the dllstorage attribution which is required
to get the symbol exported properly.

Author: compnerd

stdlib/public/Concurrency/Debug.h

@@ -25,11 +25,11 @@ namespace swift {
 // dispatch.
 
 /// The metadata pointer used for job objects.
-SWIFT_RUNTIME_STDLIB_SPI
+SWIFT_EXPORT_FROM(swift_Concurrency)
 const void *const _swift_concurrency_debug_jobMetadata;
 
 /// The metadata pointer used for async task objects.
-SWIFT_RUNTIME_STDLIB_SPI
+SWIFT_EXPORT_FROM(swift_Concurrency)
 const void *const _swift_concurrency_debug_asyncTaskMetadata;
 
 } // namespace swift