modprobe: shouldn't load kernel modules from /system

Kernel modules are not permitted to be on /system partition.
That was one of Treble requirements in O:
https://source.android.com/devices/architecture/kernel/modular-kernels#file-locations

Bug: 74069409
Test: pixel/nexus devices don't have LKMs in /system, so this change
shoudl be harmless.
Test: walleye boots without issues from modprobe.
Merged-In: I8b3aeb55aacb3c99e0486224161d09a64bb52cd1
Change-Id: I8b3aeb55aacb3c99e0486224161d09a64bb52cd1

(cherry picked from commit 6ef9f5232e7b86ff61388295139e0ae00000de7a)
diff --git a/public/modprobe.te b/public/modprobe.te
index 7d9e05d..1190409 100644
--- a/public/modprobe.te
+++ b/public/modprobe.te
@@ -7,5 +7,3 @@
   allow modprobe rootfs:system module_load;
   allow modprobe rootfs:file r_file_perms;
 ')
-allow modprobe { system_file }:system module_load;
-r_dir_file(modprobe, { system_file })