Add missing '$' character in docblock for DrupalWebTestCase::drupalGetNodeByTitle() function.

Attached one-line patch fixes what I am sure is a simple typographical error:

--- a/modules/simpletest/drupal_web_test_case.php
+++ b/modules/simpletest/drupal_web_test_case.php
@@ -845,7 +845,7 @@ class DrupalWebTestCase extends DrupalTestCase {
   /**
    * Get a node from the database based on its title.
    *
-   * @param title
+   * @param $title
    *   A node title, usually generated by $this->randomName().
    * @param $reset
    *   (optional) Whether to reset the internal node_load() cache.