Flutter has deprecated using apply plugin for its gradle plugin, and it issues a warning if you try to use it. This cleans up the use of apply plugin from all of our example and test projects.
Additionally, switch the Dart language version to "<4.0.0", as that is how Dart is interpreting it anyway (and publishing it as is right now is issuing a warning).
refs: RUM-3500
Review checklist
[ ] This pull request has appropriate unit and / or integration tests
[ ] This pull request references a Github or JIRA issue
What and why?
Flutter has deprecated using
apply pluginfor its gradle plugin, and it issues a warning if you try to use it. This cleans up the use ofapply pluginfrom all of our example and test projects.Additionally, switch the Dart language version to "<4.0.0", as that is how Dart is interpreting it anyway (and publishing it as is right now is issuing a warning).
refs: RUM-3500
Review checklist