OpenAI embeder from langchain has more options than chroma

[PranavPuranik]

🐛 Describe the bug

We should be importing the embedder for openai from langchain not chromadb - https://github.com/embedchain/embedchain/blob/main/embedchain/embedder/openai.py#L4

Openai vs chromadb funciton

It gives us more flexibility to call the openai embedding functionality over current implementation of chroma - especially http proxy settings.

[tanmaysankhe]

I will work on this.

[Dev-Khant]

@tanmaysankhe Feel free to work on this.