Update homebrew release docs.
Update homebrew release docs.

`brew bump-formula-pr` has simplified the process for updating brew
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justinsb/kops,chrislovecnm/kops,pdh/kops,tsupertramp/kops,tsupertramp/kops,pdh/kops,blakebarnett/kops,andrewsykim/kops,mad01/kops,aledbf/kops,robinpercy/kops,robinpercy/kops,mad01/kops,kubernetes/kops,pdh/kops,gambol99/kops,robinpercy/kops,gambol99/kops,aledbf/kops,andrewsykim/kops,mad01/kops,chrislovecnm/kops,blakebarnett/kops,aledbf/kops,robinpercy/kops,gambol99/kops,blakebarnett/kops,blakebarnett/kops,tsupertramp/kops,andrewsykim/kops,justinsb/kops,kubernetes/kops,gambol99/kops,pdh/kops,aledbf/kops,chrislovecnm/kops,justinsb/kops,kubernetes/kops,mad01/kops,tsupertramp/kops,andrewsykim/kops,chrislovecnm/kops