docs: Elaborate on CUBEJS_TOUCH_PRE_AGG_TIMEOUT

Author: paveltiunov

docs/pages/product/configuration/reference/environment-variables.mdx

@@ -1357,6 +1357,7 @@ Required port to send where collector server accept UDP connections.
 <WarningBox>
 
 If the refresh worker’s throughput isn’t sufficient and the Cube Refresh Worker can’t refresh every partition, Cube will start dropping partitions once the timeout is reached.
+For externally refreshed pre-aggregations, make sure each pre-aggregation is refreshed at least once within the specified timeout period.
 
 </WarningBox>
 
@@ -1807,4 +1808,4 @@ The port for a Cube deployment to listen to API connections on.
 [ref-folders]: /product/data-modeling/reference/view#folders
 [ref-dataviz-tools]: /product/configuration/visualization-tools
 [ref-context-to-app-id]: /product/configuration/reference/config#context_to_app_id
-[ref-environments]: /product/workspace/environments
+[ref-environments]: /product/workspace/environments