Update 2-hydration.html.md

[matiastucci]

This change is 

[purplecabbage]

This is a markdown file, so you can't just put the link in there. I think the better solution is to just remove the {:target} all together.

Great discussion on this here: https://github.com/mojombo/github-flavored-markdown/issues/28 Or in context => here{:target="_blank"}