hardware.bluetooth: fix configuration directory mode (#396044)

Changed files
+1
nixos
modules
services
hardware
+1
nixos/modules/services/hardware/bluetooth.nix
···
CapabilityBoundingSet = [
"CAP_NET_BIND_SERVICE" # sockets and tethering
];
+
ConfigurationDirectoryMode = "0755";
NoNewPrivileges = true;
RestrictNamespaces = true;
ProtectControlGroups = true;