issue template: don't recommend ROS Answers any more (#381)

Refer users to Robotics Stack Exchange instead.

Signed-off-by: gavanderhoorn <[email protected]>

.github/ISSUE_TEMPLATE.md

@@ -1,5 +1,5 @@
 <!--
-For general questions, please ask on ROS answers: https://answers.ros.org, make sure to include at least the `ros2` tag and the rosdistro version you are running, e.g. `ardent`.
+For general questions, please ask on ROS answers: https://robotics.stackexchange.com, make sure to include at least the `ros2` tag and the rosdistro version you are running, e.g. `ardent`.
 For general design discussions, please post on discourse: https://discourse.ros.org/c/ng-ros
 Not sure if this is the right repository? Open an issue on https://github.com/ros2/ros2/issues
 For Bug report or feature requests, please fill out the relevant category below