Remove IKMarkerTask defaulted copy ctor

[adamkewley]

Produces warnings in clang13 because it's a pattern that is formally deprecated. See:

https://stackoverflow.com/questions/51863588/warning-definition-of-implicit-copy-constructor-is-deprecated

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This change is 

[aymanhab]

This could be problematic to the GUI if removed since the SWIG bindings may not be generated if there's no copy constructor, will need to investigate further.

[adamkewley]

It should generate one implicitly - unless a member variable has no copy constructor (the previous version shouldn't have compiled in that case).

The other alternative is to explicitly default the copy assignment operator (effectively, add that declaration). I think either way would work but it might be that not supplying anything also has the side-effect of implicitly generating the move ctor/assignment (unsure about this)

[adamkewley]

Merging this straggler: SWIG will certainly generate a copy constructor for the bindings, even if one is not explicitly declared (as in this PR). Otherwise, a large amount of OpenSim code will not work (many components etc. implicitly define the constructor).

[aymanhab]

@adamkewley Unfortunately this commit broke the GUI build on ci because the copy constructor was not generated. I understand why you'd think this should work except for the fact that the GUI doesn't do much model building while it creates/copies/manipulates all kinds of tools/tasks and many of these are on the old property system so they may not act as expected. I can try to modify the GUI code base in the future but for now I'd appreciate if you'd revert this change. Thank you

[adamkewley]

Reverted.

Sorry for the mixup Ayman - it is kind of bonkers that SWIG wouldn't generate a copy constructor for a class that automatically has one (in terms of C++) :<.

[aymanhab]

No problem at all @adamkewley and thanks for the prompt response 👍