JS: Removed some unused code from EntityPallet
JS: Removed some unused code from EntityPallet

Follow-up to commit:
692e20973b9e1e4ba873144e5de7740b7d13c04a (JS: remove ability to generate object thumbnails by off-screen rendering)

Signed-off-by: Stephen Wong <6f34db11dd2258ec4ffa799eb0d7827f906cb1c6@ausenco.com>

jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim