Update common.mdx (#2099)

typo

website/content/docs/configuration/events/common.mdx

@@ -20,7 +20,7 @@ These parameters are shared across all sink types:
   not specified a default source will be composed of the
   https://hashicorp.com/boundary.io/ServerName/Path/FileName.
 
-- `allow_filters` - Specifies a set predicates for including an event in the
+- `allow_filters` - Specifies a set of predicates for including an event in the
   sink. If any filter matches, the event will be included. For more information,
   on using filters see: [event filtering](/docs/concepts/filtering/events)