wpa_supplicant: Remove unnecessary permissions from system_server

Now that the android wifi framework has fully switched over to HIDL,
remove the sepolicy permissions for accessing wpa_supplicant using
socket control interface.

While there, also removed the redundant |hwbinder_use|.

Bug: 35707797
Test: Device boots up and able to connect to wifi networks.
Test: Wifi integration tests passed.
Change-Id: I55e24b852558d1a905b189116879179d62bdc76c