[Wi-Fi] Remove redundant code in WifiSettings2

WifiPickerTracker get WifiEntries at onStart, it's no meaning
to getWifiEntry at WifiSettings2#onActivityCreated.

Bug: 143328194
Test: manual
      Edit a Wi-Fi network by clicking context menu 'Modify',
      rotate the WiFiDialog and see if any thing wrong

Change-Id: I9746879720b72723259e1b59e8b5e8bae183b8cc