manifest: sync with android-9.0.0_r6

Change-Id: If6c2c324defae6ded3e5f0d511a7e65b61f564b8

default.xml

@@ -3,7 +3,7 @@
   <remote  name="aosp"
            fetch="https://android.googlesource.com"
            review="https://android-review.googlesource.com/" />
-  <default revision="refs/tags/android-9.0.0_r3"
+  <default revision="refs/tags/android-9.0.0_r6"
            remote="aosp"
            sync-c="true"
            sync-j="12" />