docs for flutter packages doesn't have links to api.dartlang.org

[jonasfj]

https://pub.dartlang.org/documentation/image_picker/latest/image_picker/ImagePicker-class.html

This is after we filter libraries such as dart:*.

[jcollins-g]

Unfortunately this is a side effect of the workaround for dart-lang/dartdoc#1972. If we fix that and remove the workaround, Dartdoc should again be able to tie this all together.

[mit-mit]

Assigning to @jcollins-g as this is blocked on a dartdoc issue