prezto: Update links to the new community home of prezto
prezto: Update links to the new community home of prezto

sorin-ionescu/prezto is an abandoned project, the new living community
fork is on zsh-users organisation now.

Refs: https://github.com/sorin-ionescu/prezto/issues/1239

voronkovich/awesome-zsh-plugins,unixorn/awesome-zsh-plugins