RichDecodedData: remove duplicate ID assert

Turns out, in real data this does happen (very rarely) presumably due to some low level corruption, due to bit flips in data (e.g. from radiation).

Allowing duplicate hits through is not an issue downstream in the reco, it will just use both copies blindly and thus make duplicate photons for the same hit. Always running a dupe check to remove them is not worth the CPU cost involved.

So just remove as its no longer completely impossible.

FYI @rmatev