Docs: Correct `@since` tag for the `class-wp-widget-area-customize-control.php` file.

Per the documentation standards, the file header `@since` tag is supposed to specify when the file was introduced.

Follow-up to [35389].

See #51800.
Built from https://develop.svn.wordpress.org/trunk@49678


git-svn-id: http://core.svn.wordpress.org/trunk@49401 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/customize/class-wp-widget-area-customize-control.php

@@ -4,7 +4,7 @@
  *
  * @package WordPress
  * @subpackage Customize
- * @since 3.4.0
+ * @since 4.4.0
  */
 
 /**

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.7-alpha-49677';
+$wp_version = '5.7-alpha-49678';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.