Merge pull request #19744 from totten/master-upg-cleanup

release#16 - Cleanup empty upgrade steps

CRM/Upgrade/Incremental/sql/5.6.beta2.mysql.tpl

-{* file to handle db changes in 5.6.beta2 during upgrade *}

CRM/Upgrade/Incremental/sql/5.7.0.mysql.tpl

-{* file to handle db changes in 5.7.0 during upgrade *}

CRM/Upgrade/Incremental/sql/5.7.alpha1.mysql.tpl

-{* file to handle db changes in 5.7.alpha1 during upgrade *}

CRM/Upgrade/Incremental/sql/5.8.beta1.mysql.tpl

-{* file to handle db changes in 5.8.beta1 during upgrade *}

CRM/Upgrade/Incremental/sql/5.9.0.mysql.tpl

-{* file to handle db changes in 5.9.0 during upgrade *}