fix(common): Remove unused import

[crawford]

Moving the import under the tty-emitter feature fixes the following:

warning: unused import: `IsTerminal`
  --> /home/user/swc/crates/swc_common/src/errors/emitter.rs:15:28
   |
15 |     io::{self, prelude::*, IsTerminal},
   |                            ^^^^^^^^^^
   |
   = note: `#[warn(unused_imports)]` on by default

[changeset-bot]

🦋 Changeset detected

Latest commit: 92053dc

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[codspeed-hq]

CodSpeed Performance Report

Merging #9387 will degrade performances by 5.46%

_{Comparing crawford:compile-warning (92053dc) with main (4e854c7)}

Summary

❌ 2 regressions
✅ 176 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	crawford:compile-warning	Change
❌	es/full/bugs-1	541 µs	572.2 µs	-5.46%
❌	es/full/codegen/es2015	275.5 µs	290.5 µs	-5.18%