[11.x] fix PHPDoc for \Illuminate\Database\Connection (#53212)

* fix phpdoc * fix int -> float

Author: taka-oyama

src/Illuminate/Database/Connection.php

@@ -106,7 +106,7 @@ class Connection implements ConnectionInterface
  /**
  * The event dispatcher instance.
  *
- * @var \Illuminate\Contracts\Events\Dispatcher
+ * @var \Illuminate\Contracts\Events\Dispatcher|null
  */
  protected $events;
 
@@ -127,7 +127,7 @@ class Connection implements ConnectionInterface
  /**
  * The transaction manager instance.
  *
- * @var \Illuminate\Database\DatabaseTransactionsManager
+ * @var \Illuminate\Database\DatabaseTransactionsManager|null
  */
  protected $transactionsManager;
 
@@ -865,7 +865,7 @@ public function logQuery($query, $bindings, $time = null)
  /**
  * Get the elapsed time since a given starting point.
  *
- * @param int $start
+ * @param float $start
  * @return float
  */
  protected function getElapsedTime($start)