chore: completely deprecate counter system  #74

We deprecated the counter system in favor of native inline disable support in ERBLint in: v0.2.0.

To ease migration of counters, we supported allowing the counter system to be enabled on a per rule basis through a config.

Now that we're a few versions in and we expect consumers to have migrated away from counters following the migration guide that was previously shared, let's completely deprecate the counter system.