We reverted !5146 (merged) in !5245 (merged) due to a migration timeout. We need to include this in a release when we find a suitable workaround.
cc @vsizov @rymai
UPDATE from @vsizov: According to @stanhu 's research we don't need the default value for lock_version column in rails 5.x. So we probably need to revert it when we are on rails 5