Fix build error: restore deleted image with new name

The image subscriptions.png was incorrectly flagged as orphaned due to a
case mismatch (file was lowercase, reference was Subscriptions.png).
Restored as subscription-filter.png and updated the reference.

Co-authored-by: Copilot <[email protected]>

Author: msmbaldwin

articles/key-vault/key-vault-insights-overview.md

@@ -148,7 +148,7 @@ There's a limit of 200 key vaults that can be selected and viewed. Regardless of
 
 We only show subscriptions that contain key vaults, chosen from the selected subscription filter, which are selected in the "Directory + Subscription" in the Azure portal header.
 
-![Screenshot of subscription filter](./media/key-vaults-insights-overview/Subscriptions.png)
+![Screenshot of subscription filter](./media/key-vaults-insights-overview/subscription-filter.png)
 
 ### I want to make changes or add more visualizations to Key Vault Insights, how do I do so