security: remove deprecated CommandInterestSigner

Change-Id: I3b59362a4486f49559f834381a2ba63108e4dee3
diff --git a/docs/release-notes/release-notes-0.5.1.rst b/docs/release-notes/release-notes-0.5.1.rst
index 63c831f..033a6bd 100644
--- a/docs/release-notes/release-notes-0.5.1.rst
+++ b/docs/release-notes/release-notes-0.5.1.rst
@@ -23,7 +23,7 @@
   * New security-supporting utilities: trust anchor container and certificate cache
   * Creation of `Command Interests
     <https://redmine.named-data.net/projects/ndn-cxx/wiki/CommandInterest>`__ delegated to
-    :ndn-cxx:`CommandInterestSigner` class, while the new KeyChain only :doc:`signs Interests
+    ``CommandInterestSigner`` class, while the new KeyChain only :doc:`signs Interests
     </specs/signed-interest>` (:issue:`3912`)
 
 - Enable validator to fetch certificates directly from the signed/command interest sender