Remove "directLink" prop (#488)

Is not required anymore since "Link" of react-router-dom is a "<a>" element now anyway.
It also caused the following warning

"react-dom.development.js:86  Warning: React does not recognize the `directLink` prop on a DOM element. If you intentionally want it to appear in the DOM as a custom attribute, spell it as lowercase `directlink` instead. If you accidentally passed it from a parent component, remove it from the DOM element"

src/screens/settings/Backup.tsx

@@ -161,7 +161,7 @@ export function Backup() {
     return (
         <>
             <List sx={{ padding: 0 }}>
-                <ListItemLink to={requestManager.getExportBackupUrl()} directLink>
+                <ListItemLink to={requestManager.getExportBackupUrl()}>
                     <ListItemText
                         primary={t('settings.backup.label.create_backup')}
                         secondary={t('settings.backup.label.create_backup_info')}