Bundled Themes: Standardize the Required PHP and Tested Up To headers.

This change makes several changes to ensure consistency and accuracy for default theme headers:

- Removes `WordPress` from `Requires at least` headers.
- Ensures the `Requires at least` and `Requires PHP` headers are present in every default theme’s `style.css` file.
- Ensures `Tested up to` is present in every `readme.txt` file.
- Removes any headers not processed in both the `style.css` and `readme.txt` files for each theme.

Props Otto42, afragen.
Fixes #48517.
Built from https://develop.svn.wordpress.org/trunk@46676


git-svn-id: http://core.svn.wordpress.org/trunk@46476 1a063a9b-81f0-0310-95a4-ce76da25c4cd

readme.txt

@@ -1,8 +1,6 @@
 === Twenty Twelve ===
 Contributors: wordpressdotorg
-Requires at least: WordPress 3.5
-Tested up to: WordPress 5.0
-Requires PHP: 5.2.4
+Tested up to: 5.0
 Stable tag: 3.0
 License: GPLv2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html

style.css

@@ -5,6 +5,8 @@ Author: the WordPress team
 Author URI: https://wordpress.org/
 Description: The 2012 theme for WordPress is a fully responsive theme that looks great on any device. Features include a front page template with its own widgets, an optional display font, styling for post formats on both index and single views, and an optional no-sidebar page template. Make it yours with a custom menu, header image, and background.
 Version: 3.0
+Requires at least: 3.5
+Requires PHP: 5.2.4
 License: GNU General Public License v2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html
 Tags: blog, one-column, two-columns, right-sidebar, custom-background, custom-header, custom-menu, editor-style, featured-images, flexible-header, footer-widgets, full-width-template, microformats, post-formats, rtl-language-support, sticky-post, theme-options, translation-ready