Fix alias syntax

This MR is to fix the following error.

In file included from /cvmfs/atlas.cern.ch/repo/sw/software/25.0/Athena/25.0.25/InstallArea/x86_64-el9-gcc13-opt/src/Tracking/TrkVertexFitter/TrkVKalVrtFitter/TrkVKalVrtFitter/TrkVKalVrtFitter.h:20:
In file included from /cvmfs/atlas.cern.ch/repo/sw/software/25.0/Athena/25.0.25/InstallArea/x86_64-el9-gcc13-opt/src/MagneticField/MagFieldConditions/MagFieldConditions/AtlasFieldCacheCondObj.h:11:
In file included from /cvmfs/atlas.cern.ch/repo/sw/software/25.0/Athena/25.0.25/InstallArea/x86_64-el9-gcc13-opt/src/MagneticField/MagFieldElements/MagFieldElements/AtlasFieldCache.h:19:
In file included from /cvmfs/atlas.cern.ch/repo/sw/software/25.0/Athena/25.0.25/InstallArea/x86_64-el9-gcc13-opt/src/MagneticField/MagFieldElements/MagFieldElements/AtlasFieldMap.h:18:
In file included from /cvmfs/atlas.cern.ch/repo/sw/software/25.0/Athena/25.0.25/InstallArea/x86_64-el9-gcc13-opt/src/MagneticField/MagFieldElements/MagFieldElements/BFieldCache.h:21:
/global/homes/t/toyamaza/workdir/wplusD_SS/CharmAnalysis/25.0.25/CharmAnalysis/athena/Control/CxxUtils/CxxUtils/vec.h:166:9: error: using declaration requires a qualified name
  using type vec_fb<T, N>;
        ^
/global/homes/t/toyamaza/workdir/wplusD_SS/CharmAnalysis/25.0.25/CharmAnalysis/athena/Control/CxxUtils/CxxUtils/vec.h:166:13: error: expected ';' after using declaration
  using type vec_fb<T, N>;
            ^
            ;
/global/homes/t/toyamaza/workdir/wplusD_SS/CharmAnalysis/25.0.25/CharmAnalysis/athena/Control/CxxUtils/CxxUtils/vec.h:207:1: error: no type named 'type' in 'CxxUtils::vecDetail::vec_typedef<double, 8>'
using vec = typename vecDetail::vec_typedef<T,N>::type;
^~~~~
/cvmfs/atlas.cern.ch/repo/sw/software/25.0/Athena/25.0.25/InstallArea/x86_64-el9-gcc13-opt/src/MagneticField/MagFieldElements/MagFieldElements/BFieldCache.h:41:33: note: in instantiation of template type alias 'vec' requested here
  void setField(const CxxUtils::vec<double, 8>& field1,
                                ^

Control/CxxUtils/CxxUtils/vec.h

@@ -163,7 +163,7 @@ struct vec_typedef {
 #if HAVE_VECTOR_SIZE_ATTRIBUTE
   using type __attribute__((vector_size(N * sizeof(T)))) = T;
 #else
-  using type vec_fb<T, N>;
+  using type = vec_fb<T, N>;
 #endif
 };