Cleanup: Anim, re-word the explanation of the term 'binding'

Re-word the explanation of 'binding', as the old explanation was still
based on the old name 'output'.

No functional changes.

source/blender/animrig/ANIM_animation.hh

@@ -185,8 +185,8 @@ ENUM_OPERATORS(Layer::Flags, Layer::Flags::Enabled);
  * to identify which F-Curves (and in the future other animation data) it will
  * be animated by.
  *
- * This is called an 'binding' because it acts like an binding socket of the
- * Animation data-block, into which an animatable ID can be noodled.
+ * This is called a 'binding' because it binds the animatable ID to the sub-set
+ * of animation data that should animate it.
  *
  * \see AnimData::binding_handle
  */