[examples] Only enable makeFastAMG in version >=2.10

examples/utilities.hh

@@ -145,6 +145,7 @@ void incorporateEssentialConstraints(const Basis& basis, Matrix& matrix, Vector&
 
 
 
+#if DUNE_VERSION_GTE(DUNE_ISTL, 2, 10)
 /**
  * \brief Create a FastAMG preconditioner
  * \tparam Matrix Type of the matrix the preconditioner should act on.
@@ -187,6 +188,7 @@ auto makeAMGPreconditioner(const Matrix& matrix, const Vector& dummy)
 {
   return makeAMGPreconditioner<Vector>(matrix);
 }
+#endif