Remove mentioning shaded dependencies (#271)

## Checklist before submitting

- [X] Did you read the [contributing
guide](https://github.com/G-Research/spark-dgraph-connector/blob/contributing-guidelines/CONTRIBUTING.md)?
- [X] Did you update the docs?
- [ ] Did you write any tests to validate this change?  

## Description

Shaded dependencies have been removed in v0.9.0 already.

## Review process for approval

1. All tests and other checks must succeed.
2. At least one core contributors must review and approve.
3. If a core contributor requests changes, they must be addressed.