graphics/alembic: unbreak the fetch and drop needless LIB_DEPENDS

• Distfile had been rerolled upstream to remove experimental tweak that accidentally snuck its way in (diff-verified)
• Do not force linking against science/libaec' which is not used directly and could only be pulled via optional science/hdf5', where it is also subject to SZIP option

Reported by: vvd, pkg-fallout, Mamoru Iwaki
PR: 282157, 281999 (first take)