[Docs] Dartdoc links are not working for ScriptCategory

[justinmc]

This sort of comment is not resulting in a link:

/// [ScriptCategory.englishLike]

Also, the analyzer doesn't complain about it. Is this user-error somehow or is there a bug here?

Discovered in #165395.

[Renzo-Olivares]

Similarly /// [SelectableRegionSelectionStatus.finalized] does not work in https://api.flutter.dev/flutter/widgets/SelectableRegion-class.html even though its defined in the same file it is used in.

[Mastermind-sap]

I believe there is a problem with generating links to enum values.
There has been a lot of issues with dartdoc generating broken links for enum values. (referring previous issues : 1, 2, 3)