Reporter: remove redundant property

This property was introduced in commit 9eaaccd (March 2014) and made redundant in commit f61025c (March 2015) by the introduction of the `Util\Timing` class. It hasn't been used since.

Time to remove this dead wood.

Author: jrfnl

src/Reporter.php

@@ -60,13 +60,6 @@ class Reporter
      */
     public $totalFixed = 0;
 
-    /**
-     * When the PHPCS run started.
-     *
-     * @var float
-     */
-    public static $startTime = 0;
-
     /**
      * A cache of report objects.
      *