We are retiring the Activity column in OneDrive and Shared Libraries. The feature, in its current state, is not providing the intended value and experience. If your organization is not using the Activity column you can safely disregard this message.
[How does this affect me?]
When the feature is removed, the Activity Column in OneDrive and Shared Libraries will no longer be visible.
To view recent activity, by yourself or others, use the Activities section in the Details Pane for a selected file or folder.
[What do I need to do to prepare?]
You may consider updating your training and documentation as appropriate.