Fix flaky time-based spec using be_within matcher

What does this MR do and why?

(Hopefully 🤞) Fixes a flaky time-based spec by using the be_within matcher and a small number of seconds:

expect(Date.current).to be_within(5.seconds).of(today + 3.days)

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

Resolves #345345 (closed)