fix: issue with custom parsing function handling in DocusaurusLoader __init__

[a-klos]

This pull request refactors the initialization logic in the Docusaurus document loader to improve clarity and handle the parsing_function parameter more explicitly.

Refactoring for clarity:

• libs/community/langchain_community/document_loaders/docusaurus.py: Refactored the __init__ method to explicitly retrieve and remove the parsing_function from kwargs before passing it to the superclass, ensuring cleaner and more readable code.

[a-klos]

fixes the issue described here:

#113