Remove torch:: namespace reference from LLaMMARunner.mm (#5516)

Summary:
examples/ code should use the new `executorch::` namespaces.

Pull Request resolved: #5516

Test Plan: Built the app using the instructions at https://github.com/pytorch/executorch/blob/main/examples/demo-apps/apple_ios/LLaMA/README.md

Reviewed By: larryliu0820

Differential Revision: D63138639

Pulled By: dbort

fbshipit-source-id: fffb6d35d425dd733eead1b24ee8b9f2831e65c0

examples/demo-apps/apple_ios/LLaMA/LLaMARunner/LLaMARunner/Exported/LLaMARunner.mm

@@ -12,7 +12,8 @@
 #import <executorch/examples/models/llama2/runner/runner.h>
 #import <executorch/examples/models/llava/runner/llava_runner.h>
 
-using namespace ::torch::executor;
+using executorch::extension::llm::Image;
+using executorch::runtime::Error;
 
 NSErrorDomain const LLaMARunnerErrorDomain = @"LLaMARunnerErrorDomain";
 NSErrorDomain const LLaVARunnerErrorDomain = @"LLaVARunnerErrorDomain";