Fixed inaccuracy in "Built-in permalink styles" docs [skip ci]
Fixed inaccuracy in "Built-in permalink styles" docs [skip ci]

Must be either:

> Rather than typing `permalink: /:categories/:year/:month/:day/:title/`, you can just type `permalink: pretty`.

or:

> Rather than typing `permalink: /:categories/:year/:month/:day/:title.html`, you can just type `permalink: date`.

I guess the former was meant to write because the latter was already mentioned in "Where to configure permalinks" section.
rlugojr/jekyll,x-way/jekyll,gencer/jekyll,jaybe-jekyll/jekyll,chrisfinazzo/jekyll,fulldecent/jekyll,getandpost/jekyll.github.io,alex-kovac/jekyll,jaybe-jekyll/jekyll,alex-kovac/jekyll,tomjohnson1492/jekyll,jekyll/jekyll,alex-kovac/jekyll,chrisfinazzo/jekyll,tillgrallert/jekyll,fulldecent/jekyll,tomjohnson1492/jekyll,ryanshaw/jekyll,rasa2011/rasa2011.github.io,rasa2011/rasa2011.github.io,getandpost/jekyll.github.io,Strangehill/jekyll,gencer/jekyll,tomjohnson1492/jekyll,rlugojr/jekyll,tomjohnson1492/jekyll,gencer/jekyll,getandpost/jekyll.github.io,xiebinhqy/jklly_china,ryanshaw/jekyll,tillgrallert/jekyll,alex-kovac/jekyll,rlugojr/jekyll,Strangehill/jekyll,tillgrallert/jekyll,Strangehill/jekyll,jekyll/jekyll,jekyll/jekyll,fulldecent/jekyll,x-way/jekyll,fulldecent/jekyll,ryanshaw/jekyll,xiebinhqy/jklly_china,xiebinhqy/jklly_china,jaybe-jekyll/jekyll,yhironaka/yhironaka.github.io,Strangehill/jekyll,ryanshaw/jekyll,x-way/jekyll,xiebinhqy/jklly_china,tomjohnson1492/jekyll,rasa2011/rasa2011.github.io,alex-kovac/jekyll,jaybe-jekyll/jekyll,chrisfinazzo/jekyll,rlugojr/jekyll,gencer/jekyll,x-way/jekyll,gencer/jekyll,chrisfinazzo/jekyll,tillgrallert/jekyll,tillgrallert/jekyll,Strangehill/jekyll,jekyll/jekyll