Removed nonexistent LoopOnceClamp.

src/animation/AnimationMixer.js

@@ -738,7 +738,6 @@ THREE.AnimationMixer._Action.prototype = {
 		switch ( loop ) {
 
 			case THREE.LoopOnce:
-			case THREE.LoopOnceClamp:
 
 				if ( loopCount === -1 ) {