Delete unused step definitions

Running cucumber with the "-f stepdefs" flag will output all the step definitions, outlining how long each took. This can be used to identify the steps that are never run, hence can be removed.

It's interesting to see which steps take the longest and just how long they take. Two of the steps in the `audit_trail_steps.rb` file take over 10 seconds each!

Full output here: https://gist.github.com/tekin/76858a12e5f5403c8115

Note: only useful on a single-process test run as the steps will get counted separately in a parallel test run, so the numbers will be out.