Remove batchingOomAdj Flag

Delete usage/reference of this batching flag. Mantain the behavior that
allows to enable/disable of OOM batching through `adb shell setprop`.

Test: m
Test: Verified lmkd receives batching OOM requests
Bug: 409605284
Change-Id: I2bfd2599a37964a69c60a7fd004852a4aaf9db44
Signed-off-by: Carlos Galo <carlosgalo@google.com>
Flag: EXEMPT removing batching_oom_adj
[ Fix trivial conflict in flags.aconfig - Kalesh Singh ]
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>