docs: update several URLs to point to docs.named-data.net

Change-Id: If000753573c6a50130dc3101a411b6d482ccf3ed
diff --git a/docs/index.rst b/docs/index.rst
index 70f99fe..df9f084 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -65,7 +65,7 @@
 Issues
 ------
 
-Please submit any bugs or feature requests to the
+Please submit any bug reports or feature requests to the
 `ndn-cxx issue tracker <https://redmine.named-data.net/projects/ndn-cxx/issues>`__.
 
 License