Reverse change to minimum version for reduction clause

While this was introduced in OpenMP 5.0 for taskloop, it has not
previously been restricted and is irrelevant to adding support in
flang. If we want to restrict this, we should do it in a separate
patch.

Author: Stylie777

llvm/include/llvm/Frontend/OpenMP/OMP.td

@@ -1291,7 +1291,7 @@ def OMP_TaskLoop : Directive<[Spelling<"taskloop">]> {
                         VersionedClause<OMPC_Mergeable>,
                         VersionedClause<OMPC_NoGroup>,
                         VersionedClause<OMPC_Private>,
-                        VersionedClause<OMPC_Reduction, 50>,
+                        VersionedClause<OMPC_Reduction>,
                         VersionedClause<OMPC_Shared>,
                         VersionedClause<OMPC_Untied>,
   ];