[Fix] Change cohere model and library

[valentimarco]

Description

Should fix the problem?? idk langchain is strange...

What i done is:

• Change where we import the model, from langchain-community to langchain-cohere

Also remove some unused modules

Related to issue #843

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas

[dave90]

Tested the fix using a Cohere trial key and confirmed that the cat is now working correctly :)

[pieroit]

Thanks @valentimarco @dave90 , merging into develop