PLT-5873 Renamed private groups to private channels (#5924)

* PLT-5873 Renamed private groups to private channels in web app

* PLT-5873 Renamed private groups to private channels in server

webapp/components/suggestion/search_suggestion_list.jsx

@@ -33,7 +33,7 @@ export default class SearchSuggestionList extends SuggestionList {
             text = (
                 <FormattedMessage
                     id='suggestion.search.private'
-                    defaultMessage='Private Groups'
+                    defaultMessage='Private Channels'
                 />
             );
         }