Resolve prelude redundant import warnings

    warning: the item `FromIterator` is imported redundantly
       --> src/mapping.rs:10:5
        |
    10  | use std::iter::FromIterator;
        |     ^^^^^^^^^^^^^^^^^^^^^^^
        |
       ::: nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/prelude/mod.rs:129:13
        |
    129 |     pub use core::prelude::rust_2021::*;
        |             ------------------------ the item `FromIterator` is already defined here
        |
        = note: `#[warn(unused_imports)]` on by default

    warning: the item `FromIterator` is imported redundantly
       --> src/value/from.rs:148:5
        |
    148 | use std::iter::FromIterator;
        |     ^^^^^^^^^^^^^^^^^^^^^^^
        |
       ::: nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/prelude/mod.rs:129:13
        |
    129 |     pub use core::prelude::rust_2021::*;
        |             ------------------------ the item `FromIterator` is already defined here

src/mapping.rs

@@ -7,7 +7,6 @@ use std::cmp::Ordering;
 use std::collections::hash_map::DefaultHasher;
 use std::fmt::{self, Display};
 use std::hash::{Hash, Hasher};
-use std::iter::FromIterator;
 use std::mem;
 
 /// A YAML mapping in which the keys and values are both `serde_yaml::Value`.

src/value/from.rs

@@ -145,8 +145,6 @@ impl<'a, T: Clone + Into<Value>> From<&'a [T]> for Value {
     }
 }
 
-use std::iter::FromIterator;
-
 impl<T: Into<Value>> FromIterator<T> for Value {
     /// Convert an iteratable type to a YAML sequence
     ///