Improve Instruction Fine-Tuning Documentation on AWS Jumpstart

### Product Category

JumpStart

### Feedback Category

Clarity and Comprehensibility, Missing Examples and Tutorials

### Reference Link

_No response_

### Details

It would be beneficial to clearly state if pre-processing of samples is necessary (any special tokens that need to be inserted for Mixtral 8x7b) / how the expected samples should look like. Also, the layout is messed up.

Start by locating the AWS JumpStart instruction fine-tuning documentation for Mixtral 8x7b and inspect its current layout and sample guidance. Clarify whether preprocessing and special tokens are required, show the expected sample format, and correct the layout; done means the page answers these questions clearly and renders properly.

Written by the indexing model from the issue text.