Consider project as refreshing when the refresh is running

What does this MR do and why?

Change the condition of Project#refreshing_build_artifacts_size? from build_artifacts_size_refresh&.started? to build_artifacts_size_refresh&.running?.

Project#refreshing_build_artifacts_size? is used to guard against job artifact deletion when the project build artifacts size is being refreshed.

The refresh states are created, running, and pending. It is in running when a worker is actively working on the refresh. If the worker cannot complete the refresh within the given batch, it will put it into pending, which is a dormant state until the refresh is picked up again by the next worker.

In the previous implementation of Project#refreshing_build_artifacts_size?, it lead to significant blockage on DestroyBatchService which deletes artifacts on schedule.

This blockage happens even though the BuildArtifactSizeRefresh of the project is in pending.

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Related to #332994 (closed)