[Glitch] Ensure tabIndex is number instead of string

Port ec0c104bf2 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/features/local_settings/navigation/item/index.jsx

@@ -60,7 +60,7 @@ export default class LocalSettingsPage extends React.PureComponent {
       <a
         onClick={handleClick}
         role='button'
-        tabIndex='0'
+        tabIndex={0}
         className={finalClassName}
         title={title}
         aria-label={title}