Redundant coverage flag

Defined here: https://gitlab.eclipse.org/eclipse/aidge/aidge_core/-/blob/dev/CMakeLists.txt?ref_type=heads#L174-176

And here: https://gitlab.eclipse.org/eclipse/aidge/aidge_core/-/blob/dev/CMakeLists.txt?ref_type=heads#L51-53

One of the line should be removed (I think the last one)