Fix undocumented exceptions and deprecate URLRequired

[dosine-staging]

This pull request addresses issue psf#6877 by updating the documentation to include previously undocumented exceptions in the Requests library. The following changes have been made:

1. Documentation Update: Added documentation for various exceptions that were not previously listed, ensuring that users have access to complete information about the exceptions they may encounter.

2. Deprecation of URLRequired: The URLRequired exception has been deprecated and removed from the codebase, as it was not being raised anywhere. A note has been added to the documentation indicating its deprecation, while maintaining backward compatibility for users who may still rely on it.

These changes improve the clarity and accuracy of the Requests library documentation, helping users to better understand the exceptions that can be raised during usage.

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This pull request was co-created with Cosine Genie

Original Task: swe-requests/j1sk7x9nsne1
Author: Sam Stenner