Remove unnecessary group from blank_screen.

Was accidentally copy-pasted here.

Bug: N/A
Test: setprop ctl.start blank_screen
Change-Id: I0b100b02aecd2649f2528834f431a0bc8b164c46
diff --git a/light/utils/blank_screen.rc b/light/utils/blank_screen.rc
index 735551c..7b2a55e 100644
--- a/light/utils/blank_screen.rc
+++ b/light/utils/blank_screen.rc
@@ -1,5 +1,5 @@
 service blank_screen /system/bin/blank_screen
     user system
     oneshot
-    group system readproc
+    group system
     shutdown critical