Wrong indentation around trait bounds for output parameters.

[mookid]

See #306.

Minimal reproduction:

pub fn f<Req, Resp>() -> MR<
    impl FnMut(ServiceResponse) -> Resp,
>
where
    Req: Send,
    Resp: Send,
{
}

get reindented to

pub fn f<Req, Resp>() -> MR<
    impl FnMut(ServiceResponse) -> Resp,
    >
where
    Req: Send,
Resp: Send,
{
}