Don't drop time from timelogs.spent_at

What does this MR do?

At the moment we drop the time, and only record the date a timelog was spent at. This MR retains the time by no longer dropping it.

Previously, timelog system notes looked like:

Adding the time made them look "event worse":

So this MR also removes the unnecessary repetition of the date/time the spent time was logged at:

If time is added retrospectively, we still show the date:

As a follow up, we should probably consider supporting retrospective time logging with date and time (currently date only).

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

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