Revert "[flang] OpenMP allocate directive parse tree fix"

This reverts commit eaf7d97865.
Arcanist stripped co-author data from initial commit.

flang/lib/Parser/unparse.cpp

@@ -2325,14 +2325,6 @@ public:
     EndOpenMP();
   }
   void Unparse(const OpenMPExecutableAllocate &x) {
-    const auto &fields =
-        std::get<std::optional<std::list<parser::OpenMPDeclarativeAllocate>>>(
-            x.t);
-    if (fields) {
-      for (const auto &decl : *fields) {
-        Walk(decl);
-      }
-    }
     BeginOpenMP();
     Word("!$OMP ALLOCATE");
     Walk(" (", std::get<std::optional<OmpObjectList>>(x.t), ")");