examples: Fix config llama3

[JohanWork]

Description

chat_template shouldn't be set in the datasets in accordans with https://axolotl-ai-cloud.github.io/axolotl/docs/config.html, you set it in the outer level. It is set correctly at line 9.

Motivation and Context

Cleaning up the config

How has this been tested?

Screenshots (if appropriate)

Types of changes

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