Remove deprecated get_attribute_for_oid method

[alex]

No description provided.

[Copilot]

Pull Request Overview

This PR removes the deprecated get_attribute_for_oid method from the CertificateSigningRequest binding, updates tests to drop deprecation warnings, and records the removal in the changelog.

• Drop all test cases that validated the old deprecation path.
• Remove the Rust implementation and import of the deprecated method.
• Document the backward-incompatible removal in CHANGELOG.rst.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tests/x509/test_x509.py	Removed tests wrapping request.get_attribute_for_oid in warnings
src/rust/src/x509/csr.rs	Deleted the get_attribute_for_oid method and its import
CHANGELOG.rst	Added note about removing the deprecated method

Comments suppressed due to low confidence (2)

tests/x509/test_x509.py:1

• Remove the import of utils.DeprecatedIn36 (and related warning imports) since all tests referencing the deprecated method have been removed.

import utils

tests/x509/test_x509.py:6854

• Add a new test asserting that calling request.get_attribute_for_oid now raises an AttributeError, to ensure the deprecated method is fully removed from the public API.

assert request.attributes.get_attribute_for_oid(