iOS: Default to the Vulkan backend

Core/Config.cpp

@@ -448,13 +448,18 @@ static int DefaultGPUBackend() {
 		return (int)GPUBackend::VULKAN;
 	}
 #endif
+
 #elif PPSSPP_PLATFORM(MAC)
+
 #if PPSSPP_ARCH(ARM64)
 	return (int)GPUBackend::VULKAN;
 #else
 	// On Intel (generally older Macs) default to OpenGL.
 	return (int)GPUBackend::OPENGL;
 #endif
+
+#elif PPSSPP_PLATFORM(IOS_APP_STORE)
+	return (int)GPUBackend::VULKAN;
 #endif
 
 	// TODO: On some additional Linux platforms, we should also default to Vulkan.