exclusion is not supported by notification filters (#692)

* exclusion is not supported by custom filters

* Update content/github/managing-subscriptions-and-notifications-on-github/managing-notifications-from-your-inbox.md

Co-authored-by: hubwriter <hubwriter@github.com>

Co-authored-by: hubwriter <hubwriter@github.com>

Author: mchelen-gov

content/github/managing-subscriptions-and-notifications-on-github/managing-notifications-from-your-inbox.md

@@ -82,6 +82,7 @@ Custom filters do not currently support:
   - Distinguishing between the `is:issue`, `is:pr`, and `is:pull-request` query filters. These queries will return both issues and pull requests.
   - Creating more than 15 custom filters.
   - Changing the default filters or their order.
+  - Search [exclusion](/github/searching-for-information-on-github/understanding-the-search-syntax#exclude-certain-results) using `NOT` or `-QUALIFIER`.
 
 ### Supported queries for custom filters