Turbopack + Relay: don’t manually provide a fallback artifact_directo…

…ry (#8660)

`swc_relay` implements its own logic for locating the `__generated__`
directory relative to the input file[0]

Test Plan: `TURBOPACK_BUILD=1 TURBOPACK=1 pnpm test-dev
test/integration/relay-graphql-swc-single-project/test/index.test.js`

[0]
https://github.com/swc-project/plugins/blob/8c1c1513b9d445e27d47407a9a3dea4fc53e185a/packages/relay/transform/src/lib.rs#L250-L254

crates/turbopack-ecmascript-plugins/src/transform/relay.rs

@@ -73,18 +73,9 @@ impl CustomTransformer for RelayTransformer {
  .context("Expected relative path to relay artifact")?,
  );
 
- let config = if self.config.artifact_directory.is_some() {
- self.config.clone()
- } else {
- swc_relay::Config {
- artifact_directory: Some(PathBuf::from("__generated__")),
- ..self.config
- }
- };
-
  let p = std::mem::replace(program, Program::Module(Module::dummy()));
  *program = p.fold_with(&mut swc_relay::relay(
- &config,
+ &self.config,
  FileName::Real(PathBuf::from(ctx.file_name_str)),
  path_to_proj,
  // [TODO]: pages_dir comes through next-swc-loader