fix typo

src/iter/mod.rs

@@ -1126,7 +1126,7 @@ pub trait ParallelIterator: Sized + Send {
  /// multiple sums. The number of results is nondeterministic, as
  /// is the point where the breaks occur.
  ///
- /// So if did the same parallel fold (`fold(0, |a,b| a+b)`) on
+ /// So if we did the same parallel fold (`fold(0, |a,b| a+b)`) on
  /// our example list, we might wind up with a sequence of two numbers,
  /// like so:
  ///