[SettingsLib] Fix WPA2 security type string

WPA2 security string was incorrect, set to WPA2-PSK instead of RSN-PSK.
This caused a lot of error logs, as well as inaccurate description of
the connected network in the Network details dialog.

Bug: 130147064
Test: adb logcat | grep SettingsLib.AccessPoint and verify no error logs
Test: Verify correct security detail in Network details dialog
Change-Id: Iea57985c73b26fc38061694a76fd51ab578ea692