Modifying engine cart CI build parameterization

At present, EngineCart's parsing of `.engine_cart.yml` will overwrite
the `ENGINE_CART_RAILS_OPTIONS` set in CircleCI (see
[cbeer/engine_cart/102][1] for some details). The present overwrite
behavior is reasonable. As the removed `.engine_cart.yml` targeted
pre-Rails 5 behavior, I opted to remove it.

In doing so, this would now "activate" the `.circleci/config.yml`
declaration of `ENGINE_CART_RAILS_OPTIONS`. As we have coffee script in
Hyrax (for better or worse) and we have ActionCable usage, I needed to
revisit the now activated parameters. The parameters to which I changed
are the defaults of EngineCart (as of this PR).

Note: This is in preparation for allowing PostgreSQL as the database
for CircleCI.

As this impacts the `.internal_test_app` generation, I also needed to
bump the Regen number.

TL;DR: A 4 year old file that we no longer need is silently trampling
on a CI variable. That CI variable has likely not been used. It now will
be used, but needed modifications to reflect that usage.

_I hope this works, as iterating on the CI process is always time
consuming as it requires coordination of remote resources._

[1]:cbeer/engine_cart#102

.circleci/config.yml

@@ -64,7 +64,7 @@ jobs:
     environment:
       RAILS_VERSION: << parameters.rails_version >>
       NOKOGIRI_USE_SYSTEM_LIBRARIES: true
-      ENGINE_CART_RAILS_OPTIONS: --skip-git --skip-bundle --skip-listen --skip-spring --skip-yarn --skip-keeps --skip-action-cable --skip-coffee --skip-puma --skip-test
+      ENGINE_CART_RAILS_OPTIONS: --skip-git --skip-bundle --skip-listen --skip-spring --skip-keeps --skip-test --skip-bootsnap
     steps:
       - attach_workspace:
           at: ~/

.regen

@@ -1 +1 @@
-5
+9