Ignore Flutter Web source context error in Sentry Frontend for internal dart files

[buenaflor]

Description

frontend shows misleading error: missing source content for internal dart files

this is not useful and should be ignored, especially since the user application code source context is working

ignore:

• org-dartlang-sdk:///dart-sdk/lib/async/future_impl.dart
• org-dartlang-sdk:///dart-sdk/lib/async/zone.dart

[vaind]

Should we move this to the UI repo?

[buenaflor]

no need, I'll make a quick fix, I already did this in the frontend a couple months back for other files with the same misleading error