Misc doc edits for release

howto/code/linting.rst
======================
  o fixed a typo

release_notes/voltha_2.12.rst
=============================
  o Update kafka URLs

Change-Id: Iac34d06b7cd9c4342263f80a0db040a1aa06a614
diff --git a/howto/code/linting.rst b/howto/code/linting.rst
index e500f4c..aaba632 100644
--- a/howto/code/linting.rst
+++ b/howto/code/linting.rst
@@ -1,4 +1,4 @@
-.. _code--makefile-lint-targets
+.. _code--makefile-lint-targets:
 
 ======================================
 Makefile Lint Targets: Syntax Checking