Avoid false test failures due to network conditions in the `WP_REST_Plugins_Controller_Test` class. This mocks HTTP responses from the plugin information endpoint for the link-manager plugin.
Props: peterwilsoncc, costdev.
See #59647.
git-svn-id: https://develop.svn.wordpress.org/trunk@57531 602fd350-edb4-49c9-b593-d223f7449a82