Remove Davidvlu from amcl and costmap packages (#284)

nav2_amcl/package.xml

@@ -18,7 +18,6 @@
   <url>http://wiki.ros.org/amcl</url>
   <author>Brian P. Gerkey</author>
   <author>contradict@gmail.com</author>
-  <maintainer email="davidvlu@gmail.com">David V. Lu!!</maintainer>
   <maintainer email="mfergs7@gmail.com">Michael Ferguson</maintainer>
   <maintainer email="ahoy@fetchrobotics.com">Aaron Hoy</maintainer>
   <maintainer email="mohammad.haghighipanah@intel.com">Mohammad Haghighipanah</maintainer>

nav2_costmap_2d/package.xml

@@ -12,7 +12,6 @@
     costmap, rolling window based costmaps, and parameter based subscription to
     and configuration of sensor topics.
   </description>
-  <maintainer email="davidvlu@gmail.com">David V. Lu!!</maintainer>
   <maintainer email="mfergs7@gmail.com">Michael Ferguson</maintainer>
   <maintainer email="ahoy@fetchrobotics.com">Aaron Hoy</maintainer>
   <maintainer email="stevenmacenski@gmail.com">Steve Macenski</maintainer>