Revert dependency on go.uber.org/atomic

[aknuds1]

We should revert dependency on go.uber.org/atomic instead of the standard sync/atomic package. It's a follow-up to #836, and based on the same logic we should avoid forcing the dependency on go.uber.org/atomic also. See #836 for context.

From Slack:

@aknuds1:

Given the same logic, should I revert also my PR switching us over to go.uber.org/atomic dims?

@dims:

yes please!