Add template keyword for dependent Data member

Author: amandalund

src/celeritas/optical/gen/OffloadGatherAction.hh

@@ -94,7 +94,7 @@ class OffloadGatherAction final : public CoreStepActionInterface,
     //// TYPES ////
 
     template<Ownership W, MemSpace M>
-    using Data = typename TraitsT::Data<W, M>;
+    using Data = typename TraitsT::template Data<W, M>;
     using Executor = typename TraitsT::Executor;
 
     //// DATA ////