Remove ember-classic-decorator package for Ember 5 compatibility

[gokolo]

While upgrading our app to Ember 5.4.0 we encountered errors originating from ember-light-table's use of ember-classic-decorator. We found that the ember-classic-decorator package is not compatible with Ember 5.x.
See this Discord thread for more context.

Opened a PR to remove it from the ember-light-table to make it work on Ember 5 projects.

Also found that ember-scrollable also uses ember-classic-decorator.
A reminder that the forked version of ember-scrollable by @RobbieTheWagner used in ember-light-table's has not been merged upstream yet.