Enhance max_execution_time documentation with link

Updated the explanation of the max_execution_time setting to include a link to the documentation. Also clarify it's in seconds.

Author: MikeShi42

knowledgebase/query_max_execution_time.mdx

@@ -14,7 +14,7 @@ How do I enforce a time limit on my queries?
 
 ## Answer \{#answer\}
 
-You can use `max_execution_time` setting:
+You can use [`max_execution_time`](https://clickhouse.com/docs/operations/settings/settings#max_execution_time) setting (expressed in seconds):
 
 ```sql
 clickhouse-cloud :) SELECT 1 SETTINGS max_execution_time=0.0001