Remove extra spaces from start_ursim statement in tests ( backport of #1010)

With those extra spaces the input isn't correctly parsed.

Author: mergify[bot]

ur_robot_driver/test/test_common.py

@@ -273,8 +273,7 @@ def _ursim_action():
                     "start_ursim.sh",
                 ]
             ),
-            " ",
-            "-m ",
+            "-m",
             ur_type,
         ],
         name="start_ursim",