Fix import and init issue with using OpenAIEmbeddings

[willtai]

Description

This PR fixes a few issues regarding using the package's OpenAIEmbedding class:

• Allow embedding model name to be specified correctly and used
• Removed sentence_transformers from embeddings/__init__.py to avoid ImportError if sentence_transformers` package is not installed, which is meant to be an optional dependency.

Type of Change

• New feature
• Bug fix
• Breaking change
• Documentation update
• Project configuration change

Complexity

Complexity: Low

How Has This Been Tested?

• Unit tests
• E2E tests
• Manual tests

Checklist

The following requirements should have been met (depending on the changes in the branch):

• Documentation has been updated
• Unit tests have been updated
• E2E tests have been updated
• Examples have been updated
• New files have copyright header
• CLA (https://neo4j.com/developer/cla/) has been signed
• CHANGELOG.md updated if appropriate

[willtai]

@CodiumAI-Agent /update_changelog

[CodiumAI-Agent]

Changelog updates: 🔄

2024-07-09

Fixed

• Resolved import issues with OpenAIEmbeddings class.
• Corrected initialization to allow specifying the embedding model name.
• Removed sentence_transformers from embeddings/__init__.py to avoid ImportError when the package is not installed.

to commit the new content to the CHANGELOG.md file, please type:
'/update_changelog --pr_update_changelog.push_changelog_changes=true'

[stellasia]

Thanks for the fixes!