Remove broken code

In d9876b84 this was moved from Incident/LinkArticles.html to
Link/Articles.html with the commit message:

   move LinkArticles.html into more natural location.
   it's not only about incidents

It left hardcoded "Link selected articles to Incident $ticket->Id" even
when run from an IR or an Investigation.

Additionally, it didn't work. It submitted to "Display.html" which
doesn't exist now that it was moved from RTIR/Incident/ into Link/

So, delete this.  Users can instead use the core 'Extract Article' code
which we'll stop from being deleted out of the menu in RTIR and they can
link an Article either from the Article UI or by replying to a message
and using an Article, like core articles has worked for years.

I can see some argument for wanting to link an article to an incident to
indicate the Article used to solve it, but that hasn't worked in any
RTIR 3 release and we have no bug reports, so we'll see if it shows up
as a feature request once it goes missing.

Resolves issues #29961
Resolves issues #29962
Don't offer Create/Link options

Link was broken (didn't work after it was moved to work on things other
than Incidents) and Create is silly since it doesn't even let you
leverage core's Extract Article UI.
Bring in the core feature to extract an article

This is better than RTIR's "Create" article link which drops you into
the Article creation page and makes you copy and paste the wording you
liked, rather than just using the extract UI.
The extract UI could use some love, but has existed for years.
Actually record the article link when using one on a reply.

The other Reply pages (IR and Investigations) do this because they're
closer to core.  This reply page totally ignores it.

It would be good to also record article links on the children where this
article is used, but it requires a bit of args tweaking.
Use content_like, which provides a readable test failure
We're no longer testing a link from the IR to Article Creation

Use the first article create, create the IR, make sure the box shows up.
We should test Extract Article, but that's really mocking core, while
this tests that the box shows up for RTIR.
Match the core rename
No longer display the Articles titlebox unless articles are linked

Now that we no longer have Create/Link action links, we can safely hide
the box unless someone has added a link to an article to the ticket.
Merge branch '3.2/clean-up-articles-code'