build: update waf to version 2.0.24

Change-Id: I57b597fb5933e46b55979ad6b1a62a7fd40c645d
diff --git a/docs/release-notes/release-notes-0.6.0.rst b/docs/release-notes/release-notes-0.6.0.rst
index 34e44e3..e843b62 100644
--- a/docs/release-notes/release-notes-0.6.0.rst
+++ b/docs/release-notes/release-notes-0.6.0.rst
@@ -37,8 +37,7 @@
 
 - Advisory limit of ``NameTree`` depth (:issue:`4262`)
 
-- `Contributing guide <https://github.com/named-data/NFD/>`__ and `code of conduct
-  <https://github.com/named-data/NFD/>`__ (:issue:`3898`)
+- Contributor's Guide and Code of Conduct (:issue:`3898`)
 
 Updates
 ^^^^^^^