doc: fix CHANGELOG.md table formatting

* It had some minor errors in td/th html tags.
* Make it clear that v5, v0.10, and v0.12 are EOL and unsupported.

We probably don't want people seeing 'LTS' badge next to those
in the current Node.js repo and think that those are still supported.
Not everyone is aware of the nodejs/LTS repo.

This also includes the dates for v5, v0.10 and v0.12 EOL:
 - 2016-07-01 for v5
 - 2016-11-01 for v0.10
 - 2017-01-01 for v0.12

* Make v5/v0.10/v0.12 not bold in CHANGELOG

Make v5, v0.10, v0.12 not bold in the CHANGELOG.md, as bold is said to
be an indication of the most recent actively supported release futher
on the same page.

PR-URL: https://github.com/nodejs/node/pull/10743


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>