delete vestigial assertion in NumberPicker that fails on !options, https://github.com/phetsims/area-model-common/issues/5
delete vestigial assertion in NumberPicker that fails on !options, https://github.com/phetsims/area-model-common/issues/5

Signed-off-by: Chris Malley <74b2712074b149d140079dbd7e875955d192e617@pixelzoom.com>

phetsims/scenery-phet,phetsims/scenery-phet,phetsims/scenery-phet