Use $DISPLAY rather than assuming :0 (#2049) (#2365)

* Use $DISPLAY rather than assuming :

* Double quotes

---------

Co-authored-by: Sebastian Jahr <sebastian.jahr@picknik.ai>
(cherry picked from commit 2fa4667)

Co-authored-by: Stephanie Eng <stephanie-eng@users.noreply.github.com>

moveit_configs_utils/moveit_configs_utils/launches.py

@@ -1,3 +1,5 @@
+import os
+
 from launch import LaunchDescription
 from launch.actions import (
     DeclareLaunchArgument,
@@ -237,7 +239,7 @@ def generate_move_group_launch(moveit_config):
         parameters=move_group_params,
         extra_debug_args=["--debug"],
         # Set the display variable, in case OpenGL code is used internally
-        additional_env={"DISPLAY": ":0"},
+        additional_env={"DISPLAY": os.environ["DISPLAY"]},
     )
     return ld