Makes use of markdownlint for automated cleanup

Because for now, we're changing the format.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1751

Update the links in all docs except user and admin pages

Because the left nav is changing
and will have a button instead
of carat, and no magnifying glass.

Related to: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/127935

Because we changed the way we
do the markdown.

Related to: https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1690

https://gitlab.com/gitlab-org/gitlab/-/issues/416175#note_1488040590

This refactors the GitLab for Jira app docs to have a clear "configure"
section, distinct from the "installation" section, as people can
configure the app after the initial installation.

It adds information that the initial data sync happens in batches.

- Update references of "namespace" to "group" to avoid
confusion for users.
- Update "add" to "link".
- Use a consistent translation namespace "JiraConnect"
throughout the app.

Changelog: changed

It changes the current JiraConnectApp error message to be more user
friendly. Additionally, it adds a link to the relevant
Troubleshooting page.

Changelog: changed

and don't repeat

This removes the feature flag `jira_connect_oauth`.
The feature's been enabled 7 months ago.

Changelog: other

List ways of installing Jira Cloud

Updates the historic data synchronization and
the feature comparison table.