Update comments and document in since annotation

Author: sirreal

src/wp-includes/customize/class-wp-customize-custom-css-setting.php

@@ -145,14 +145,14 @@ public function value() {
 	}
 
 	/**
-	 * Validate a received value for being valid CSS.
+	 * Validate a received value for being safe HTML STYLE tag contents.
 	 *
-	 * Checks for imbalanced braces, brackets, and comments.
 	 * Notifications are rendered when the customizer state is saved.
 	 *
 	 * @since 4.7.0
 	 * @since 4.9.0 Checking for balanced characters has been moved client-side via linting in code editor.
 	 * @since 5.9.0 Renamed `$css` to `$value` for PHP 8 named parameter support.
+	 * @since 7.0.0 Relaxed to only check for safe HTML STYLE tag contents.
 	 *
 	 * @param string $value CSS to validate.
 	 * @return true|WP_Error True if the input was validated, otherwise WP_Error.

src/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-controller.php

@@ -659,10 +659,11 @@ public function get_theme_items( $request ) {
 	/**
 	 * Validate style.css as valid CSS.
 	 *
-	 * Currently just checks for invalid markup.
+	 * Currently just checks that CSS will not break an HTML STYLE tag.
 	 *
 	 * @since 6.2.0
 	 * @since 6.4.0 Changed method visibility to protected.
+	 * @since 7.0.0 Relaxed to only check for safe HTML STYLE tag contents.
 	 *
 	 * @param string $css CSS to validate.
 	 * @return true|WP_Error True if the input was validated, otherwise WP_Error.