Revert "Bump messages from 19.1.4 to 20.0.0"
Revert "Bump messages from 19.1.4 to 20.0.0"

This reverts commit 9672e0cfec1d1bd28cdf0e3bbfb4e2cf7a876c0e.

apache/isis,apache/isis,apache/isis,apache/isis,apache/isis,apache/isis