fix(notification): don't remove file based notifier on start up (#1862)

Attempting to run Authelia with least privilege principle as the `nobody` user and a file based notifier will cause issues during start up as the user cannot remove the notification file.

Given that ioutil.WriteFile truncates the file before writing the removal should not be necessary.

Fixes #1846.

internal/notification/file_notifier.go

@@ -37,10 +37,6 @@ func (n *FileNotifier) StartupCheck() (bool, error) {
 		if !os.IsNotExist(err) {
 			return false, err
 		}
-	} else {
-		if err = os.Remove(n.path); err != nil {
-			return false, err
-		}
 	}
 
 	if err := ioutil.WriteFile(n.path, []byte(""), fileNotifierMode); err != nil {