All Ember Try Scenarios should run if one fails

[jelhan]

This pull requests enables continue-on-error for all Ember Try Scenarios. So far it was only set to true for scenarios, which were allowed to fail in Travis CI configuration.

Travis CI's allow-failure option and GitHub Action's continue-on-error option are not comparable:

• The allow-failure option of Travis CI affects the result of the CI pipeline. The CI pipeline is still considered as successful even if a job, which allow-failure: true, is failed.
• The continue-on-error option provided by GitHub Action does not affect the result of the CI pipeline. A pipeline is considered as failing if any job fails. Regardless if continue-on-error is true or false for the job. Instead the option controls if subsequent jobs are executed or not.

The difference between both and the need for an option like Travis CI's allow-failure in GitHub Actions is discussed in this thread: https://github.com/actions/runner/issues/2347

It makes sense to run all Ember Try Scenarios always regardless if one fails:

• It will often be very helpful for debugging to know which Ember Try Scenarios pass and which are failing. Therefore it makes sense to run them all regardless if one already failed.
• Having continue-on-error: true reduces complexity and prevents certain edge cases by design (#43).
• The only downside, which I'm aware of, is more workload caused by CI. This may affect budget for private projects and may be bad from climate perspective.

Fixes actions/toolkit#43