Docs: Add a missing @since version to the DocBlock for wp_add_dashboard_widget().

See #32246.

Built from https://develop.svn.wordpress.org/trunk@36878


git-svn-id: http://core.svn.wordpress.org/trunk@36845 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/dashboard.php

@@ -132,7 +132,9 @@ function wp_dashboard_setup() {
 /**
  * Adds a new dashboard widget.
  *
- * @global array   $wp_dashboard_control_callbacks
+ * @since 2.7.0
+ *
+ * @global array $wp_dashboard_control_callbacks
  *
  * @param string   $widget_id        Widget ID  (used in the 'id' attribute for the widget).
  * @param string   $widget_name      Title of the widget.