Fix connected wifi entry not clearing when Wifi is disabled

Connected wifi entry is represented by either
mConnectedWifiEntryPreferenceCategory or
mFirstWifiEntryPreferenceCategory, but we only clear
mConnectedWifiEntryPreferenceCategory when Wifi is disabled. Make sure
to also clear mFirstWifiEntryPreferenceCategory.

Bug: 267815756
Test: manually verify connected wifi is hidden when wifi is disabled
Change-Id: I4c30a658200f1ab90af5ce41a6531f5784a8de5d