1.8 release notes correctly note `replace --force`
1.8 release notes correctly note `replace --force`

`kops replace --create` was replaced with `kops replace --force`, but
the release notes were not updated to match this.

When merging, https://github.com/kubernetes/kops/releases/tag/1.8.0 should be
manually updated to match this change.

fixes #4012

justinsb/kops,robinpercy/kops,gambol99/kops,kubernetes/kops,aledbf/kops,gambol99/kops,aledbf/kops,kubernetes/kops,aledbf/kops,robinpercy/kops,gambol99/kops,kubernetes/kops,blakebarnett/kops,justinsb/kops,robinpercy/kops,aledbf/kops,robinpercy/kops,blakebarnett/kops,justinsb/kops,gambol99/kops,blakebarnett/kops,blakebarnett/kops