cleanup: remove redundant TODO comment in Vector3.js (#32363)

Co-authored-by: MOHITKOURAV01 <mohitkourav@MOHITs-MacBook-Pro-2.local>
Co-authored-by: mrdoob <info@mrdoob.com>

src/math/Vector3.js

@@ -744,8 +744,6 @@ class Vector3 {
 
 	}
 
-	// TODO lengthSquared?
-
 	/**
 	 * Computes the square of the Euclidean length (straight-line length) from
 	 * (0, 0, 0) to (x, y, z). If you are comparing the lengths of vectors, you should