manifest: android-8.1.0_r20 -> android-8.1.0_r26

Change-Id: Ib0650e94563f1848b6a046a6cf758aa51044d8f8
diff --git a/default.xml b/default.xml
index bccad30..4e18e8c 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_r20" />
+           revision="refs/tags/android-8.1.0_r26" />
 
   <default revision="refs/heads/lineage-15.1"
            remote="github"