Improve Promise:U.kept/broken
Improve Promise:U.kept/broken

- Fix incorrect default value listed for .broken
- Make it easier to see .kept's default value

tbrowder/doc,perl6/doc,stmuk/doc,stmuk/doc,MasterDuke17/doc,MasterDuke17/doc,MasterDuke17/doc,MasterDuke17/doc,tbrowder/doc,stmuk/doc,perl6/doc,tbrowder/doc,perl6/doc,stmuk/doc,perl6/doc,tbrowder/doc,perl6/doc,stmuk/doc