[Wi-Fi] Remove redundant code

Should not setSummary in ConnectedWifiEntryPreference because
WifiEntryPreference updates summary by WifiEntry#getSummary

Bug: 150911380
Test: manual
      See captive portal Wi-Fi summary 'Sign in to network'
      before logging in.
Change-Id: Ibc47623d66b9d2844c0ca827081f205f0bab89e7