monitoring.yml: Use date format of go-task output for example too

Signed-off-by: Thomas Staudinger <[email protected]>

docs/packaging/monitoring.yml.md

@@ -170,7 +170,7 @@ If an established product hasn't had a security advisory in the past, it might n
 In that case, include an empty `security` and `cpe` field with a comment in the following format:
 
 ```yaml
-# No known CPE, checked 20240123
+# No known CPE, checked 2024-01-23
 security:
   cpe: ~
 ```