Fixes
https://chat.zulip.org/#narrow/channel/19-documentation/topic/new.20help.20center.3A.20Includes.20inside.20list.20item
The macro works fine for the current help center. But for the new help
center, the macro has a paragraph tag already, when it is part of a list
item, the margin inserted by starlight causes spacing issue. We can
override the margin for this specific case when we have the ability to
modify the MDX directly. Issue for that: #35407. Until then, we remove
this macro since it's only used it two places to have proper spacing.
In the help center and production documentation, replace links to
the "Getting your organization started with Zulip" guide to the
new "Moving to Zulip" guide.
These files are not Jinja2 templates, so there's no reason that they needed
to be inside `templates/zerver`. Moving them to the top level reflects their
importance and also makes it feel nicer to work on editing the help center content,
without it being unnecessary buried deep in the codebase.
