Allow shell read access to cgroup state

at /proc/cgroups.

Test: adb shell cat /proc/cgroups
Bug: 335278695
Change-Id: I52773c63200a2a048a4c5497c338ddcbe0f23593
diff --git a/private/shell.te b/private/shell.te
index 8adc71c..0fdbb7e 100644
--- a/private/shell.te
+++ b/private/shell.te
@@ -372,6 +372,7 @@
 
 allow shell {
   proc_asound
+  proc_cgroups
   proc_filesystems
   proc_interrupts
   proc_loadavg # b/124024827