gta4xl-common: Remove USE_XML_AUDIO_POLICY_CONF

* Dead since Q, where XML audio policies weren't enforced yet

Change-Id: I302a0ed97964b052176dc3bb0141db1ba85e78c8
diff --git a/BoardConfigPlatform.mk b/BoardConfigPlatform.mk
index 46415c7..609adfd 100644
--- a/BoardConfigPlatform.mk
+++ b/BoardConfigPlatform.mk
@@ -122,9 +122,6 @@
 ### USERDATA
 TARGET_USERIMAGES_USE_EXT4 := true
 
-### AUDIO
-USE_XML_AUDIO_POLICY_CONF := 1
-
 ### BLUETOOTH
 BOARD_HAVE_BLUETOOTH_SLSI := true