core: remove another compilation warning

Author: jcarpent

include/pinocchio/spatial/inertia.hpp

@@ -1,5 +1,6 @@
 //
-// Copyright (c) 2015-2021 CNRS INRIA
+// Copyright (c) 2015-2018 CNRS
+// Copyright (c) 2018-2025 INRIA
 // Copyright (c) 2016 Wandercraft, 86 rue de Paris 91400 Orsay, France.
 //
 
@@ -1210,7 +1211,7 @@ namespace pinocchio
       const Scalar exp_2d1 = exp(2 * d1);
       const Scalar exp_2d2 = exp(2 * d2);
       const Scalar exp_2d3 = exp(2 * d3);
-      const Scalar exp_d1 = exp(d1);
+      // const Scalar exp_d1 = exp(d1);
       const Scalar exp_d2 = exp(d2);
       const Scalar exp_d3 = exp(d3);