In the lifetime annotation example, add an argument label.

To clarify that the annotation refers to the parameter name, not the
label.

Author: atrick

proposals/NNNN-lifetime-dependency.md

@@ -923,7 +923,7 @@ func foo(...)
 
 ```
 @lifetime(copy arg)
-func foo(arg: Arg1) -> R {}
+func foo(label arg: Arg1) -> R {}
 ```
 
 The `.component` qualifier is only relevant once we have component lifetimes. See the "Component lifetime" section below.