perf(ir): fix benchmark import to resolve unused_import warning

Co-authored-by: Tcode-Motion <188012755+Tcode-Motion@users.noreply.github.com>

Author: google-labs-jules[bot]

compiler/ir/benches/builder_bench.rs

@@ -1,4 +1,4 @@
-use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use criterion::{criterion_group, criterion_main, Criterion};
 use techscript_ir::builder::IRBuilder;
 use techscript_ir::types::IRType;