Update supported Rails version in paranoia.gemspec

Add changelog for v2.4.3

Bump activerecord dependency for Rails 6.1

Calling `<<` to an ActiveModel::Errors message array in order to add an error is deprecated. Please call `ActiveModel::Errors#add` instead.

Update JRuby version to 9.2.8.0 + remove EOL Ruby 2.2

Fix after_commit for Rails 6

`gem update --system` fails with Ruby 2.2.

Activerecord 6 support

The versions we were running against were bumped, so we needed to update
which versions were being excluded as they were stale.

Rails master (soon to be 6.0.0) doesn't support versions before Ruby
2.5.

These versions of rails enforce this version constraint when loading the
sqlite adapter so we need to make sure that we always use a compatible
version.

Older versions of activerecord require sqlite ~> 1.3.6, but not in the
gemfile, the constraint is enforced when you load the adapter.

This allows us toe specify in the environment the version of the gem
we'd like to run against.