DO NOT MERGE ANYWHERE - Update ub-emulator-master to use main branch.

Bug: b/289400079
Change-Id: I4e71797f1a5de006707090008e187010d6008032
diff --git a/default.xml b/default.xml
index 35f73c5..a70827d 100644
--- a/default.xml
+++ b/default.xml
@@ -4,7 +4,7 @@
   <remote  name="aosp"
            fetch=".."
            review="https://android-review.googlesource.com/" />
-  <default revision="master"
+  <default revision="main"
            remote="aosp"
            sync-j="4" />