system_server: remove access sysfs_devices_system_cpu

CpuFrequency.java seems to be the only thing that depends on
/sys/devices/system/cpu in system_server. And according to
b/68988722#comment15, that dependency is not exercised.

Bug: 68988722
Test: walleye boots without denials to sysfs_devices_system_cpu
Change-Id: If777b716bf74188581327b7f5aa709f5d88aad2d

private/system_server.te

@@ -280,7 +280,6 @@ r_dir_file(system_server, sysfs_switch)
 r_dir_file(system_server, sysfs_wakeup_reasons)
 
 allow system_server sysfs_nfc_power_writable:file rw_file_perms;
-allow system_server sysfs_devices_system_cpu:file w_file_perms;
 allow system_server sysfs_mac_address:file r_file_perms;
 allow system_server sysfs_power:dir search;
 allow system_server sysfs_power:file rw_file_perms;