inter-quant-penalty in beaming

[Carl D. Sorensen]

I've been working on fixing the documentation of details for beaming.

One of the parameters in details is inter-quant-penalty.

However, this property is only read in lily/beam-quanting.cc; it is never
used.

Further, a git grep for inter-quant-penalty returns only the single
reference in lily/beam-quanting.cc.

It appears that this property is not used.  May I remove it?

Thanks,

Carl