Update 2.6 release notes with recently merged fixes

Change-Id: I65143dfa8a0ffc8f1ecd518b76d165c31f5b535b
diff --git a/ReleaseNotes/ReleaseNotes-2.6.txt b/ReleaseNotes/ReleaseNotes-2.6.txt
index 2f065b8..73d456e 100644
--- a/ReleaseNotes/ReleaseNotes-2.6.txt
+++ b/ReleaseNotes/ReleaseNotes-2.6.txt
@@ -1235,6 +1235,9 @@
 * link:https://code.google.com/p/gerrit/issues/detail?id=1915[Issue 1915]:
 Don't show non-visible drafts in the diff screens.
 
+* link:https://code.google.com/p/gerrit/issues/detail?id=1801[Issue 1801]:
+Correctly keep patch set ordering after a new patch set is added via
+the Web UI.
 
 REST API
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