chore(tier4_metrics_rviz_plugin): add kosuke55 and rej55 as maintainer (autowarefoundation#6572)

Signed-off-by: kosuke55 <kosuke.tnp@gmail.com>

Author: kosuke55

evaluator/tier4_metrics_rviz_plugin/package.xml

@@ -7,6 +7,8 @@
   <maintainer email="satoshi.ota@tier4.jp">Satoshi OTA</maintainer>
   <maintainer email="kyoichi.sugahara@tier4.jp">Kyoichi Sugahara</maintainer>
   <maintainer email="maxime.clement@tier4.jp">Maxime CLEMENT</maintainer>
+  <maintainer email="kosuke.takeuchi@tier4.jp">Kosuke Takeuchi</maintainer>
+  <maintainer email="fumiya.watanabe@tier4.jp">Fumiya Watanabe</maintainer>
   <license>Apache License 2.0</license>
 
   <buildtool_depend>ament_cmake_auto</buildtool_depend>