Remove -Wno-user-defined-warnings.

Doesn't seem to be necessary.

Bug: http://b/134716967
Test: treehugger
Change-Id: I9617cf82c816ef072005f7baf2fceee9628313f5
diff --git a/graphics/composer/2.1/utils/hwc2on1adapter/Android.bp b/graphics/composer/2.1/utils/hwc2on1adapter/Android.bp
index 420a1f6..062f2e5 100644
--- a/graphics/composer/2.1/utils/hwc2on1adapter/Android.bp
+++ b/graphics/composer/2.1/utils/hwc2on1adapter/Android.bp
@@ -20,7 +20,6 @@
     cflags: [
         "-Wall",
         "-Werror",
-        "-Wno-user-defined-warnings",
     ],
     cppflags: [
         "-Weverything",