MoveGroup naming inconsitency

[alejandrojginerd]

The MoveGroup name in hello_moveit.cpp does not match the one sued in panda.srdf, leading to errors while running ros2 run hello_moveit hello_moveit

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[sea-bass]

The main branch of this repo uses a Kinova robot which does have a manipulator group name.

I think this change is not needed, but is just a product of the robot model changing from Humble to later versions.

[mikeferguson]

Same change seems to have been suggested in a second PR here - #978 - is there something deeper going on?