Fix broken admin credentials serialization

Change-Id: Id245084e0e9df109493068de71cc73d88856041a
diff --git a/server/src/admin-config.ts b/server/src/admin-config.ts
index b52d608..0f745b9 100644
--- a/server/src/admin-config.ts
+++ b/server/src/admin-config.ts
@@ -47,6 +47,6 @@
   }
 
   async save() {
-    await writeFile(this.file, JSON.stringify(this.account) + '/n');
+    await writeFile(this.file, JSON.stringify(this.account) + '\n');
   }
 }