[DOCS] pg_replication_slots page links

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.6/static/view-pg-replication-slots.html
Description:

Hi all, 
There isn't any link between 9.4 - replication slot page and other newer
ones. 

check pages;

https://www.postgresql.org/docs/9.4/static/catalog-pg-replication-slots.html


https://www.postgresql.org/docs/current/static/view-pg-replication-slots.html

cheers