Remove USE_XML_AUDIO_POLICY_CONF build flag

This flag is no more used by the build files and should
be removed.

Bug: 132435217
Test: make
Change-Id: I55f2533b3d20ed0c8221d8ecdec744c2e71ca46a
diff --git a/emulator/audio/car_emulator_audio.mk b/emulator/audio/car_emulator_audio.mk
index bef5c2e..43d52cc 100644
--- a/emulator/audio/car_emulator_audio.mk
+++ b/emulator/audio/car_emulator_audio.mk
@@ -13,8 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-USE_XML_AUDIO_POLICY_CONF := 1
-
 PRODUCT_PACKAGES += audio.primary.caremu
 PRODUCT_PROPERTY_OVERRIDES += ro.hardware.audio.primary=caremu