[Wi-Fi] Fix 2 Wi-Fi shortcuts bug

Check feature flag to show the shortcut of
WifiSettingsActivity or WifiSettings2Activity.

Bug: 151133236
Test: manual
      Home context menu -> Widgets -> Settings shortcut
      Should only show 1 Wi-Fi shortcut option.
Change-Id: Ie980b69ce1f23614475070b5c74d9a6d5cdab7ae