Fix execute_steps() example
Fix execute_steps() example

When I tried to use `execute_steps()` as shown in the example, I was
getting an assertion about the steps needing to be in unicode.

`Assertion Failed: Steps must be unicode.`

It seems that the argument passed to `execute_steps()` must be a unicode
string otherwise it will not run.

This change updates the example for that method to show you must
provide a unicode string.

Signed-off-by: Micah Abbott <5994877adc9ac69035af1f2df439b774406830a8@redhat.com>

benthomasson/behave,jenisys/behave,jenisys/behave,Abdoctor/behave,benthomasson/behave,Abdoctor/behave