fix: slerpQuaternions doesn't return a value (#23114)

src/math/Quaternion.js

@@ -604,7 +604,7 @@ class Quaternion {
 
 	slerpQuaternions( qa, qb, t ) {
 
-		this.copy( qa ).slerp( qb, t );
+		return this.copy( qa ).slerp( qb, t );
 
 	}