Allow `wp-` prefixes on plugins

[dd32]

Per https://meta.trac.wordpress.org/ticket/5868 Using WP ... as the plugin name is allowed, but the trademark checks on WordPress.org block it preemptively.

Prefixes such as "WP .." and "WC ..." should not show as prohibited, but rather, note that they cannot be changed later to the trademarked term.

Plugin check may want to simply remove the wp- trademark check, leaving that to w.org/plugins, or may want to add a lesser-level note that it can't be changed to the trademark.

[davidperezgar]

I'd say to use a warning for that.