NonZero constructor now returns Option

[dtolnay]

rust-lang/rust#42959

error[E0308]: mismatched types
    --> src/de/impls.rs:1583:16
     |
1583 |             Ok(NonZero::new(value))
     |                ^^^^^^^^^^^^^^^^^^^ expected struct `core::nonzero::NonZero`, found enum `core::option::Option`
     |
     = note: expected type `core::nonzero::NonZero<T>`
                found type `core::option::Option<core::nonzero::NonZero<_>>`
     = help: here are some functions which might fulfill your needs:
             - .unwrap()