Update scenario to pass on Ruby 2.7
Update scenario to pass on Ruby 2.7

When running under childprocess, IRB does not activate readline. This
means history is not collected and the history file is empty if saved.
In Ruby 2.7, the file is not even written to. This means saving the
history file cannot properly be tested on Ruby 2.7 using Aruba. Instead,
we check that the correct file is configured in IRB, and just assume IRB
will do the right thing with it.

mvz/aruba,mvz/aruba,cucumber/aruba