Remove step with installing opencl_rt

[antonwolfy]

The PR proposes to get rid of installation of opencl_rt package before running tests for Windows.

The step was previously added as a workaround and isn't required anymore, since fully covered by dependent conda packages.
Removing the step will slightly speed up Conda package action.

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[github-actions]

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[vlad-perevezentsev]

LGTM!
Thank you @antonwolfy