Modernize networking layer internals for future compatibility

[emmanuel-ferdman]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

This small PR updates the internal REST client's response handling (kubernetes.client.rest.RESTResponse) to address a DeprecationWarning originating from the urllib3 library (version >= 2.0).

The underlying urllib3.HTTPResponse.getheaders() method is deprecated and scheduled for removal in urllib3 v2.1.0. This PR replaces its usage with the recommended direct access to the .headers attribute.

This change resolves the deprecation warning observed during testing and ensures future compatibility of the Kubernetes Python client with upcoming versions of urllib3.

Warning example:

/home/runner/work/python/python/kubernetes/client/rest.py:44: DeprecationWarning: HTTPResponse.getheaders() is deprecated and will be removed in urllib3 v2.1.0. Instead access HTTPResponse.headers directly.

Which issue(s) this PR fixes:

Special notes for your reviewer:

This change directly addresses the DeprecationWarning concerning HTTPResponse.getheaders() as reported in CI logs and local testing. The fix involves switching from the deprecated getheaders() method call to accessing the .headers attribute on the underlying urllib3 response object within our RESTResponse wrapper class.

Does this PR introduce a user-facing change?

NONE

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[k8s-ci-robot]

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This pull-request has been approved by: emmanuel-ferdman
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[yliaog]

the file is generated, please make any change at the generator.