Retire blank canvas (#5355)

blank-canvas/style.css

@@ -10,6 +10,7 @@ Requires PHP: 5.6.2
 Version: 1.2.9-wpcom
 License: GNU General Public License v2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html
+Status: inactive
 Template: seedlet
 Text Domain: blank-canvas
 Tags: one-column, accessibility-ready, custom-colors, editor-style, featured-images, rtl-language-support, sticky-post, translation-ready, auto-loading-homepage