manifest: android-8.1.0_r11 -> android-8.1.0_r15

Change-Id: I85c2ddb4a056e1a1b5e0063def45f6a89c83c2f0
diff --git a/default.xml b/default.xml
index f4f24d1..f3cf811 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-8.1.0_r11" />
+           revision="refs/tags/android-8.1.0_r15" />
 
   <default revision="refs/heads/lineage-15.1"
            remote="github"