libsnapshot: proto use correct index

Test: pass
Bug: 154016862
Change-Id: I845d2250ddb27bdbaee0d54663a2fdb45dbfbd11
diff --git a/fs_mgr/libsnapshot/android/snapshot/snapshot.proto b/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
index 587089e..0328132 100644
--- a/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
+++ b/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
@@ -132,7 +132,7 @@
     uint64 metadata_sectors = 4;
 }
 
-// Next: 2
+// Next: 4
 message SnapshotMergeReport {
     // Status of the update after the merge attempts.
     UpdateState state = 1;
@@ -142,5 +142,5 @@
     int32 resume_count = 2;
 
     // Total size of all the COW images before the update.
-    uint64 cow_file_size = 4;
+    uint64 cow_file_size = 3;
 }