Misc doc edits for release.

release_notes/voltha_2.12.rst
-----------------------------
  o Update version and URLs for kafka
  o Update version and URLs for olt

howto/release/tasks/index.rst
howto/release/tasks/golang_gofmt_syntax.rst
-------------------------------------------
  o Document std golang formatting with gofmt -s -e -w.
  o Document content with references (commit message, make lint)
    diff --git a/howto/release/tasks/index.rst b/

Include a few edits from gerrit id I6e9658c23f436f83d423f74e01b2966943d2fe08

Change-Id: I27ad46ddd6673a9e35e794b1d3e8bb0644e8260d
8 files changed