Fix typos in copyright dates
(cherry picked from commit 3335e0767cb847154e24f5d4fa345318309d1281)
diff --git a/test/sparse_ref.cpp b/test/sparse_ref.cpp
index 12b6f8a..8f33af8 100644
--- a/test/sparse_ref.cpp
+++ b/test/sparse_ref.cpp
@@ -1,7 +1,7 @@
// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
-// Copyright (C) 20015 Gael Guennebaud <gael.guennebaud@inria.fr>
+// Copyright (C) 2015 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed