Remove methods in Article deprecated in 1.18

No uses found in core or Gerrit extensions.

* Article::doRedirect() (deprecated in 1.18)
* Article::doUnwatch() (deprecated in 1.18)
* Article::doWatch() (deprecated in 1.18)
* Article::markpatrolled() (deprecated in 1.18)
* Article::unwatch() (deprecated in 1.18)
* Article::watch() (deprecated in 1.18)

Change-Id: I37772ee08baa1d3ee15247b1c869de1299e146a6
Merge "Remove methods in Article deprecated in 1.18"