Switch to using the liboctomap-dev key for a dependency. (#5)

This is now available in rosdep.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>

package.xml

@@ -40,9 +40,7 @@
   <depend>libboost-dev</depend>
   <depend>libboost-system-dev</depend>
   <depend>libboost-regex-dev</depend>
-  <!-- Octomap is an optional dependency. There seems to be an issue resolving
-    this key on the ROS buildfarm, so disabling it for now -->
-  <!-- <depend>octomap</depend> -->
+  <depend>liboctomap-dev</depend>
   <depend>lz4</depend>
 
   <test_depend>ament_cmake_xmllint</test_depend>