cargo check: Trait objects without an explicit dyn are deprecated

[hbina]

cargo check is complaining,

warning: trait objects without an explicit `dyn` are deprecated
   --> src/division.rs:542:21
    |
542 |     writeable: &mut Write,
    |                     ^^^^^ help: use `dyn`: `dyn Write`
    |
    = note: `#[warn(bare_trait_objects)]` on by default

warning: trait objects without an explicit `dyn` are deprecated
   --> src/division.rs:756:36
    |
756 | pub fn write_digit(writeable: &mut Write, digit: u8) -> Result<bool, DivisionError>
    |                                    ^^^^^ help: use `dyn`: `dyn Write`

warning: trait objects without an explicit `dyn` are deprecated
  --> src/error.rs:56:23
   |
56 |     ExternalError(Box<Error + Send + Sync>)
   |                       ^^^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn Error + Send + Sync`

warning: trait objects without an explicit `dyn` are deprecated
   --> src/fraction/display.rs:192:45
    |
192 | pub fn format_sign(sign: Sign, buffer: &mut fmt::Write, format: &Format) -> fmt::Result {
    |                                             ^^^^^^^^^^ help: use `dyn`: `dyn fmt::Write`

warning: trait objects without an explicit `dyn` are deprecated
   --> src/fraction/display.rs:225:18
    |
225 |     buffer: &mut fmt::Write,
    |                  ^^^^^^^^^^ help: use `dyn`: `dyn fmt::Write`

warning: trait objects without an explicit `dyn` are deprecated
   --> src/fraction/display.rs:351:20
    |
351 |     V: FnOnce(&mut fmt::Write, &Format) -> Result<usize, fmt::Error>,
    |                    ^^^^^^^^^^ help: use `dyn`: `dyn fmt::Write`

warning: trait objects without an explicit `dyn` are deprecated
   --> src/fraction/display.rs:343:18
    |
343 |     buffer: &mut fmt::Write,
    |                  ^^^^^^^^^^ help: use `dyn`: `dyn fmt::Write`

    Finished dev [unoptimized + debuginfo] target(s) in 0.13s

I am not sure if it will break anything, but its quite a simple fix.

[dnsl48]

fixed by #21