manifest: android-9.0.0_r30 -> android-9.0.0_r31

Change-Id: I7a7cbb5d9389c5d5f45e0ab15b034e6cd5e57b85
diff --git a/default.xml b/default.xml
index e25770e..1f3847f 100644
--- a/default.xml
+++ b/default.xml
@@ -11,7 +11,7 @@
   <remote  name="aosp"
            fetch="https://android.googlesource.com"
            review="android-review.googlesource.com"
-           revision="refs/tags/android-9.0.0_r30" />
+           revision="refs/tags/android-9.0.0_r31" />
 
   <default revision="refs/heads/lineage-16.0"
            remote="github"