Remove unused Node.js runtime (vercel/turborepo#8398)

### Description

These files are no longer used as the "build" folder is used. That will be renamed to nodejs in a later PR in the stack.

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### Testing Instructions

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crates/turbopack-ecmascript-runtime/js/package.json

@@ -10,7 +10,6 @@
     "check:dev-client": "tsc -p src/dev/client",
     "check:dev-runtime-base": "tsc -p src/dev/runtime/base",
     "check:dev-runtime-dom": "tsc -p src/dev/runtime/dom",
-    "check:dev-runtime-nodejs": "tsc -p src/dev/runtime/nodejs",
     "check:dev-runtime-edge": "tsc -p src/dev/runtime/edge"
   },
   "exports": {

crates/turbopack-ecmascript-runtime/src/browser_runtime.rs

@@ -36,7 +36,10 @@ pub async fn get_browser_runtime_code(
         asset_context,
         match chunk_loading {
             ChunkLoading::Edge => "dev/runtime/edge/runtime-backend-edge.ts".into(),
-            ChunkLoading::NodeJs => "dev/runtime/nodejs/runtime-backend-nodejs.ts".into(),
+            // This case should never be hit.
+            ChunkLoading::NodeJs => {
+                panic!("Node.js runtime is not supported in the browser runtime!")
+            }
             ChunkLoading::Dom => "dev/runtime/dom/runtime-backend-dom.ts".into(),
         },
     );