Tweak CHANGELOG.md

(* Initial version => - Initial version)
Fixes https://github.com/google/stagehand/issues/182

`find -regex '.*/.*\.\(md\)$' | xargs sed -i s/"* Initial"/"- Initial"/g`
`grind build`

Interestingly `File.listSync()` returns different order of files between Ubuntu(mine) and Mac(yours?).
That result in huge change in `*_data.dart`. but the content is same except for (* Initial version => - Initial version)