Revert "fix right hand side scrolling over navigation"

This reverts commit e389a8ba2a79da2669b536ca242b5dfdee4faba3.

This is the commit that broke modals.

Reverting it fixes COUCHDB-2086

Fixing the right hand content overlapping the left
hand navigation will require a bigger fix...

@deathbearbrown @drsm79 @garrensmith reviews welcome. :smile: 
This sadly was not it...