AnimationMixer: Fix wrong reference count in `_bindAction()`. (#23102)

* fix: miss binding.referenceCount++ error when AnimationMixer._bindAction #23096

* Update AnimationMixer.js

Co-authored-by: wangren.wr <wangren.wr@alibaba-inc.com>
Co-authored-by: Michael Herzog <michael.herzog@human-interactive.org>

src/animation/AnimationMixer.js

@@ -48,6 +48,7 @@ class AnimationMixer extends EventDispatcher {
 
 			if ( binding !== undefined ) {
 
+				++ binding.referenceCount;
 				bindings[ i ] = binding;
 
 			} else {