doc: modules.md: fix distance definition

It's somewhat esoteric at best to define distance in terms of squared length!

Author: alexweej

doc/api/modules.md

@@ -217,7 +217,7 @@ With the following ES Modules:
 
 ```mjs
 // distance.mjs
-export function distance(a, b) { return (b.x - a.x) ** 2 + (b.y - a.y) ** 2; }
+export function distance(a, b) { return Math.sqrt((b.x - a.x) ** 2 + (b.y - a.y) ** 2); }
 ```
 
 ```mjs
@@ -269,7 +269,7 @@ export default class Point {
 
 // `distance` is lost to CommonJS consumers of this module, unless it's
 // added to `Point` as a static property.
-export function distance(a, b) { return (b.x - a.x) ** 2 + (b.y - a.y) ** 2; }
+export function distance(a, b) { return Math.sqrt((b.x - a.x) ** 2 + (b.y - a.y) ** 2); }
 export { Point as 'module.exports' }
 ```
 
@@ -293,7 +293,7 @@ named exports attached to it as properties. For example with the example above,
 <!-- eslint-disable @stylistic/js/semi -->
 
 ```mjs
-export function distance(a, b) { return (b.x - a.x) ** 2 + (b.y - a.y) ** 2; }
+export function distance(a, b) { return Math.sqrt((b.x - a.x) ** 2 + (b.y - a.y) ** 2); }
 
 export default class Point {
   constructor(x, y) { this.x = x; this.y = y; }