Remove target="_blank" from help tab in several Admin screens

[rianrietveld]

Patch removes target="_blank" from links in the help tabs in the Admin in:

• wp-admin/edit-comments.php
• wp-admin/edit-form-advanced.php
• wp-admin/edit-link-form.php
• wp-admin/edit-tags.php
• wp-admin/edit.php
• wp-admin/export.php
• wp-admin/import.php
• wp-admin/index.php
• wp-admin/link-manager.php
• wp-admin/media-new.php
• wp-admin/media.php
• wp-admin/nav-menus.php

I did not remove target="_blank" on links to Preview page/post in edit-form.advanced.php
Tracking ticket with info and discussion: #23432

[afercia]

Worth noting this patches also edit-comments.php which is already patched in #38140.

[afercia]

Needs a refresh.

[afercia]

Refreshed patch. Removes also a trailing space in a doc block.

[afercia]

In 38725:

Accessibility: Remove target=_blank from the help tab links on several admin screens.

Stop taking control of users' browsers.

Props rianrietveld.
Fixes #38145. See #23432.