You should just edit the model. Usually the spell effects are only a few kb anyway.
Get MDLX converter:
http://www.hiveworkshop.com/forums/tools-560/mdlx-converter-62991/
Extract the model from the MPQ (you can use any mpq editor on the site), and then run it through MDLX converter to get the MDL file. Open it up in notepad. There will be an animations block somewhere in there, listing "Birth", "Death", etc.. in quotes. (you can just use CTRL+F and search for "Death") Rename "Death" to something else, such as "Glababalaloobala". That is a very good name for an animation. Run it back through MDLX converter, then import the mdx in your map. Change your spell to use the imported model instead (or the effect trigger, w/e).
Anyway, theoretically this should prevent the death animation from playing when it is removed. When a spell effect is created, the engine plays the "birth" animation for its duration and then plays the "stand" animation as a loop. When a "Destroy effect" is issued, it will look for the "Death" animation. If there is none, the model will likely just disappear (iirc). There might be an issue where it just stands there for a while before disappearing--I don't quite remember. If so, you may have to resort to a different method. Try it out.