Fix document about delegate_method

[yuku]

Old spec fails with:

 Failure/Error: it { should delegate_method(:beep_boop).to(:robot).as(:speak) }
   Expected Human#beep_boop to delegate to Human#robot as #speak
   Calls on Human#robot: (none)

[mcmire]

Thanks for this. I did a big documentation update recently and made sure to take care of making sure that the documentation for delegate_method was correct. I appreciate it, though!

[yuku]

👍