Update environment.js

Simplify verbage of describe string for the framerate example.

Author: sphantom-code

src/core/environment.js

@@ -379,7 +379,7 @@ p5.prototype.cursor = function(type, x, y) {
  * function setup() {
  *   createCanvas(100, 100);
  *
- *   describe('A number written in black written on a gray background. The number decreases when the mouse is pressed.');
+ *   describe('A number written in black on a gray background. The number decreases when the mouse is pressed.');
  * }
  *
  * function draw() {