fix: the initial write does not need to be atomic

It is only written if the file does not exist due to the 'wx' flag.

packages/remix-node/sessions/fileStorage.ts

@@ -52,7 +52,7 @@ export function createFileSessionStorage({
         try {
           let file = getFile(dir, id);
           await fsp.mkdir(path.dirname(file), { recursive: true });
-          await writeFile(file, content, { encoding: "utf-8" });
+          await fsp.writeFile(file, content, { encoding: "utf-8", flag: "wx" });
           return id;
         } catch (error: any) {
           if (error.code !== "EEXIST") throw error;