Revert "transcoding: use background io priority"

This reverts commit 6beeb2ebf4ae2f5e7dc9d5861deb23de48ecfdfe.

Reason for revert: change had no effect
bug: 183751395
Change-Id: I42296ae1d1783baac879de7f4bd9141aa7be9841
diff --git a/apex/mediatranscoding.rc b/apex/mediatranscoding.rc
index 87df2d5..ae9f8ba 100644
--- a/apex/mediatranscoding.rc
+++ b/apex/mediatranscoding.rc
@@ -7,7 +7,6 @@
     group media
     ioprio rt 4
     # Restrict to little cores only with system-background cpuset.
-    # Lower IO priority to background.
-    writepid /dev/cpuset/system-background/tasks /dev/blkio/background/tasks
+    writepid /dev/cpuset/system-background/tasks
     interface aidl media.transcoding
     disabled