Remove MKL_VERSION_2024 variable from cmake files

[antonwolfy]

OneMKL 2024.0 is a minimum required version in meta.yaml as both build and run dependency.

This PR is an attempt to clean up the code and to remove a temporary solution implemented in #1567 for proper MKL discovery during the build process. As for now we should not consider a building with OneMKL < 2024.0 version.

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