terminal:remove unused parentheses

[alexs-sh]

About

This is a minor fix that removes unused parentheses and helps avoid warnings during build or when running clippy. I noticed this while working on #1011

warning: unnecessary parentheses around closure body
  --> src/terminal/sys/unix.rs:87:50
   |
87 |     let file = File::open("/dev/tty").map(|file| (FileDesc::Owned(file.into())));
   |                                                  ^                            ^
   |
   = note: `#[warn(unused_parens)]` on by default
help: remove these parentheses
   |
87 -     let file = File::open("/dev/tty").map(|file| (FileDesc::Owned(file.into())));
87 +     let file = File::open("/dev/tty").map(|file| FileDesc::Owned(file.into()));
   |

warning: `crossterm` (lib) generated 1 warning (run `cargo fix --lib -p crossterm` to apply 1 suggestion)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.18s

Versions

rustc --version
rustc 1.90.0 (1159e78c4 2025-09-14)