The tool performs various checks to determine whether or not to
regenerate version information as part of a `flutter upgrade` instead of
just regenerating `flutter.version.json` as part of each `flutter
upgrade`. This has lead to some situations where the actual framework
version doesn't match that reported by the `flutter.version.json`.
This change updates `flutter upgrade` to always regenerate
`flutter.version.json` after checking out the new version of the
framework to ensure that it contains the latest version information.
Fixes https://github.com/flutter/flutter/issues/178926
8af18377be