Recent Posts Widget: Use `ob_end_flush()` instead of `ob_flush()`.

`ob_end_flush()` flushes the output buffer *and* turns output buffering off, same as `ob_get_flush()`.

props m_i_n.
see #28009 for trunk.

Built from https://develop.svn.wordpress.org/trunk@28195


git-svn-id: http://core.svn.wordpress.org/trunk@28025 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/default-widgets.php

@@ -732,7 +732,7 @@ class WP_Widget_Recent_Posts extends WP_Widget {
 			$cache[ $args['widget_id'] ] = ob_get_flush();
 			wp_cache_set( 'widget_recent_posts', $cache, 'widget' );
 		} else {
-			ob_flush();
+			ob_end_flush();
 		}
 	}