Update Vector3.html like a grammer natzi (#9183)

GitHub makes everything so easy these days!

docs/api/math/Vector3.html

@@ -146,7 +146,7 @@
 
 		<h3>[method:Vector3 normalize]() [page:Vector3 this]</h3>
 		<div>
-		Normalizes this vector. Transforms this Vector into a Unit vector by dividing the vector by it's length.
+		Normalizes this vector. Transforms this Vector into a Unit vector by dividing the vector by its length.
 		</div>
 
 		<h3>[method:Float distanceTo]( [page:Vector3 v] ) [page:Vector3 this]</h3>