system_server: remove appdomain:file write

system_server no longer writes to /proc/pid/oom_adj_score. This is
handled exclusively by lmkd now.

See the following commits:

Kernel 3.18:
* https://android-review.googlesource.com/139083
* https://android-review.googlesource.com/139082

Kernel 3.14:
* https://android-review.googlesource.com/139081
* https://android-review.googlesource.com/139080

Kernel 3.10:
* https://android-review.googlesource.com/139071
* https://android-review.googlesource.com/139671

Kernel 3.4:
* https://android-review.googlesource.com/139061
* https://android-review.googlesource.com/139060

Bug: 19636629
Change-Id: Ib79081365bcce4aa1190de037861a87b55c15db9

system_server.te

@@ -88,9 +88,6 @@ allow system_server mediaserver:process { getsched setsched };
 # all processes on the device.
 r_dir_file(system_server, domain)
 
-# Write to /proc/pid/oom_adj_score for apps.
-allow system_server appdomain:file write;
-
 # Read/Write to /proc/net/xt_qtaguid/ctrl and and /dev/xt_qtaguid.
 allow system_server qtaguid_proc:file rw_file_perms;
 allow system_server qtaguid_device:chr_file rw_file_perms;