doc: remove "Code that grows with grace" video from front page

It was deleted from Vimeo. I will attempt to get a new version online.

Fixes #7297.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/61740043

doc/root.html

@@ -140,7 +140,6 @@ window.initFuncs.push(function() {
 	var videos = [
 		{h: 241, s: "//www.youtube.com/embed/ytEkHepK08c"}, // Tour of Go
 		{h: 241, s: "//www.youtube.com/embed/f6kdp27TYZs"}, // Concurrency Patterns
-		{h: 233, s: "//player.vimeo.com/video/53221560"},   // Grows with grace
 		{h: 233, s: "//player.vimeo.com/video/69237265"}    // Simple environment
 	];
 	var v = videos[Math.floor(Math.random()*videos.length)];