Update performance-reliability.md

revising sentence so we don't imply causal behavior

Author: satvu

articles/azure-functions/performance-reliability.md

@@ -22,7 +22,7 @@ Whenever possible, refactor large functions into smaller function sets that work
 
 ## Background tasks must complete before returning from functions
 
-Azure Functions does not track background threads. If your functions initiate any tasks, callbacks, threads, processes, tasks, etc., they must be complete before you return from your functions. If not, you risk site shutdown or other unintended behavior. 
+Azure Functions does not track background threads. If your functions initiate any tasks, callbacks, threads, processes, tasks, etc., they must be complete before you return from your functions. Site shutdown may still occur regardless of background thread status, leading to unintended behavior.
 
 For example, if a function kicks off a background task and returns a successful response before the task finishes, the function will be considered successful and complete despite the result of the background task.