ROS: fix license

Author: nim65s

package.xml

@@ -8,7 +8,7 @@
   <maintainer email="[email protected]">Guilhem Saurel</maintainer>
   <author>Justin Carpentier</author>
   <author>Nicolas Mansard</author>
-  <license>BSD</license>
+  <license>BSD-2-Clause</license>
 
   <url type="website">https://github.com/stack-of-tasks/eigenpy</url>