Description

Modify Full documentation url latest to stable in example/1-quickstart.ipynb

Motivation and Context

When I click that url

Environment, Policy and Model
Full documentation of:

Base environment class [here](https://rl4co.readthedocs.io/en/latest/_content/api/envs/base.html)
Base policy class [here](https://rl4co.readthedocs.io/en/latest/_content/api/models/base.html)
Base model class [here](https://rl4co.readthedocs.io/en/latest/_content/api/algos/base.html)

the website shows this page

this cannot access rl4co's official docs directly, so i change latest url to corresponding stable url.

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

What types of changes does your code introduce? Remove all that do not apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)
• Example (update in the folder of examples)

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.