modify quickstart example

Author: devalog

fern/products/sdks/overview/swift/quickstart.mdx

@@ -53,7 +53,7 @@ sdks/ # created by fern generate --group swift-sdk
 ├─ swift
     ├─ Package.swift
     └─ Sources
-        ├─ ApiClient.swift
+        ├─ YourClient.swift
         ├─ Schemas/
         ├─ Public/
         ├─ Core/