Remove time param in Gitlab::UsageDataCounters::EpicActivityUniqueCounter

What does this MR do?

It removes the time param from track_unique_action as it is not needed now and it defaults to Time.current in Gitlab::UsageDataCounters::HLLRedisCounter.

I considered making the param optional but as we don't use it at all I decided to remove it. We can always add the param if needed.

Does this MR meet the acceptance criteria?

Conformity

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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
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Security

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Related to #325535 (closed)