Remove setPatternFill

[juzhiyuan]

Hi @asturur, according to this issue[1], setPatternFill has been removed, and indeed it is. When I want to update this Doc site, I find it's hard because of too many codes here[2].

Not sure if there has some other way to update our doc site? and if necessary, I could help to use some tools like VuePress to rebuild this doc site.

[1] fabricjs/fabric.js#6111 (comment)
[2] https://github.com/fabricjs/fabricjs.com/blob/gh-pages/docs/fabric.Object.html#L18147

[asturur]

this files get updated automatically once the website runs on fabric 4.

A couple of demos are not ready yet for fabric 4 so i did not update the website