perf(turbopack): Update sourcemap to make flatten() faster (vercel#79297)

### What?

Update the `sourcemap` crate to the latest version.

### Why?

To apply getsentry/rust-sourcemap#121

Author: kdy1

Cargo.lock

@@ -407,7 +407,7 @@ smallvec = { version = "1.13.1", features = [
   "union",
   "const_new",
 ] }
-sourcemap = "9.0.0"
+sourcemap = "9.2.1"
 strsim = "0.11.1"
 shrink-to-fit = "0.2.10"
 swc-rustc-hash = { package = "rustc-hash", version = "1.1.0" } # used with swc