docs: Update image and text embeddings documentation

[jakmro]

Description

Changed:

• moved note about normalization
• changed CLIP model names
• changed CLIP model description
• added cosine similarity (now we don't normalize text and image embeddings by default), normalization is done inside the models

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (improves or adds clarity to existing documentation)

Checklist

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• My changes generate no new warnings