drop obsolete use of boost's _1

this relied on an implicit include of `boost/bind.hpp` from the ros_comm
headers and ROS-O changes this include due to countless downstream warnings.
ros-o/ros_comm#3

tams_pr2_gripper_action/src/pr2_gripper_action.cpp

@@ -45,8 +45,8 @@ class Pr2GripperAction
   Pr2GripperAction(ros::NodeHandle &n) :
     node_(n),
     action_server_(node_, "gripper_action",
-                   boost::bind(&Pr2GripperAction::goalCB, this, _1),
-                   boost::bind(&Pr2GripperAction::cancelCB, this, _1),
+                   [this](auto handle){ goalCB(handle); },
+                   [this](auto handle){ cancelCB(handle); },
                    false),
     has_active_goal_(false)
   {