Update workflows using Ubuntu 20.04 (focal)

[Buristan]

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Ubuntu 20.04 will soon be deprecated and unsupported in the GitHub infrastructure.

See also: https://github.com/actions/runner-images/issues/11101

So, we should update workflows, like reusable_testing.yml workflow which is used in the integraion Tarantool testing. I suppose we can update it up to 24.04 (noble).

Needed for tarantool/tarantool#11220