Clarify third lifetime elision rule example

[elardus-erasmus]

Upon first read, I stumbled over this. Talking about two input lifetimes being there already, and then Rust gives/assigns the lifetimes. I believe the proposed change clarifies/corrects the example description.

[chriskrycho]

I appreciate this (and am sorry you stumbled over it a bit!). However, I think the “input lifetimes” language is actually valuable here, since there are lots of lifetimes floating around—and while I see what you were going for with your suggested edit, I find it to be just as challenging to sort out, just… in a different way. That’s no criticism, either: this is hard to talk about. Thank you again, though!