Fix typo in DoubleEndedIterator::nth_back doc
Fix typo in DoubleEndedIterator::nth_back doc
aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust