update description for repository field

Author: bobheadxi

action.yml

@@ -52,4 +52,4 @@ inputs:
     default: 'false'
   repository:
     required: false
-    description: Set status for a different owner/repository (optional, defaults to the same repo and owner as the action)
+    description: Set status for a different repository, using the format `$owner/$repository` (optional, defaults to the current repository)