init.te: Don't allow mounting on top of /proc

Don't allow init to mount on top of /proc. See
https://android-review.googlesource.com/148295 for details.

Change-Id: I65f66b39f3a5bfb72facb9f716f4537ac2237af1
diff --git a/init.te b/init.te
index 9f68bb8..9f624ba 100644
--- a/init.te
+++ b/init.te
@@ -45,8 +45,6 @@
 allow init rootfs:dir create_dir_perms;
 allow init rootfs:dir mounton;
 
-allow init proc:dir mounton;
-
 # Mount on /dev/usb-ffs/adb.
 allow init device:dir mounton;