Removal of parent theme line in style.css

Removed "Template:" declaration line in style.css since this is not a child theme.

clean-slate/style.css

@@ -10,7 +10,6 @@ Requires PHP: 5.7
 Version: 0.0.1
 License: GNU General Public License v2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html
-Template:
 Text Domain: clean-slate
 Tags: one-column, custom-colors, custom-menu, custom-logo, editor-style, featured-images, full-site-editing, rtl-language-support, theme-options, threaded-comments, translation-ready, wide-blocks
 */