Resolve type_repetition_in_bounds clippy lint
Resolve type_repetition_in_bounds clippy lint

    error: this type has already been used as a bound predicate
       --> src/punctuated.rs:815:5
        |
    815 |     I: DoubleEndedIterator<Item = &'a T> + ExactSizeIterator<Item = &'a T> + Clone,
        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
        = note: `-D clippy::type-repetition-in-bounds` implied by `-D clippy::pedantic`
        = help: consider combining the bounds: `I: DoubleEndedIterator<Item = &'a T> + ExactSizeIterator<Item = &'a T> + Clone`
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

    error: this type has already been used as a bound predicate
       --> src/punctuated.rs:898:5
        |
    898 |     I: DoubleEndedIterator<Item = &'a mut T> + ExactSizeIterator<Item = &'a mut T>
        |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
        = help: consider combining the bounds: `I: DoubleEndedIterator<Item = &'a mut T> + ExactSizeIterator<Item = &'a mut T>`
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds

dtolnay/syn