[Keras 3 OpenVINO backend]: Support numpy.sinc operation

[goyaladitya05]

Request Description

This issue tracks adding support for numpy.sinc for the Keras OpenVINO backend.
The operation is currently not implemented in keras/backend/openvino, limiting parity for this backend.

I will submit a PR implementing this and enable the corresponding tests.

Ref: #34017

Feature Use Case

No response

Issue submission checklist

• The feature request or improvement must be related to OpenVINO