Fix regression 4688 (#4700)

Minor regression from https://github.com/FreshRSS/FreshRSS/pull/4688

app/Models/Feed.php

@@ -568,7 +568,7 @@ class FreshRSS_Feed extends Minz_Model {
 					}
 				}
 			}
-			$author_names = substr($authorNames, 0, -2);
+			$authorNames = substr($authorNames, 0, -2);
 
 			$entry = new FreshRSS_Entry(
 				$this->id(),