Remove 2.6.2 release notes from release notes index

The 2.6.2 release notes was removed in commit fc445a72 but
the link to it was not removed from the index.

Change-Id: Icd723a2c24f86e210054e248ff18c5221f796e3f
diff --git a/ReleaseNotes/index.txt b/ReleaseNotes/index.txt
index c6c45eb..28b9f65 100644
--- a/ReleaseNotes/index.txt
+++ b/ReleaseNotes/index.txt
@@ -14,7 +14,6 @@
 [[2_6]]
 Version 2.6.x
 -------------
-* link:ReleaseNotes-2.6.2.html[2.6.2]
 * link:ReleaseNotes-2.6.1.html[2.6.1]
 * link:ReleaseNotes-2.6.html[2.6]