Update Qwen README.md to remove Llama references (#15409)

There were a couple of references to Llama instead of Qwen, I believe
because we imported this file from Llama.

### Ticket
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### Problem description
Provide context for the problem.

### What's changed
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Summarize the changes made and its impact.

### Checklist
- [ ] Post commit CI passes
- [ ] Blackhole Post commit (if applicable)
- [ ] Model regression CI testing passes (if applicable)
- [ ] Device performance regression CI testing passes (if applicable)
- [ ] New/Existing tests provide coverage for changes

models/demos/qwen/README.md

@@ -53,10 +53,10 @@ The demo is also parametrized to run for 1 or 3 continuous batch of users, i.e.
 
 The input prompts are based on the general or instruct (fine-tuned) weights. The prompts are included in the demo folder `models/demos/qwen/demo`.
 
-When running the demo, do not forget to setup the `$QWEN_DIR` environment variable to the corresponding Llama3 model weights.
+When running the demo, do not forget to setup the `$QWEN_DIR` environment variable to the corresponding Qwen model weights.
 
 ```
-# Examples of how to run the demo for any supported Llama3 models
+# Examples of how to run the demo
 
 Currently, this model is only supported on N150 (single-device). If you are running this demo on a multi-chip device, please make sure FAKE_DEVICE is set to N150.