Clarify counter notice submission time/handling

Why is this change being made?

This MR is being submitted to clarify that DMCA counter notices can be submitted at any time, not just within a 10-14 day window after the initial takedown notice is shared with the subscriber.

This clarity will enable team members to handle such requests in a legally appropriate manner, as no time limitation for counter notice submission is specified within the legislation.

I'll ensure T&S team members involved in DMCA handling are looped in on this for visibility; to check if we've potentially refused counter notices in the past for being outside the accepted window of submission (risk exposure considerations); and to ensure related T&S playbooks are updated to reflect the clarified policy.

Author Checklist

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• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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