Fix invalid types in doc comments

We're on the way to psalm error level 4, but there are still some remaining issues.

lib/Internal/Producer.php

@@ -76,7 +76,7 @@ trait Producer
     /**
      * {@inheritdoc}
      *
-     * @return Promise<TValue>
+     * @return TValue
      */
     public function getCurrent()
     {

lib/Loop/NativeDriver.php

@@ -252,7 +252,7 @@ class NativeDriver extends Driver
         }
 
         if ($timeout > 0) { // Otherwise sleep with usleep() if $timeout > 0.
-            \usleep($timeout * self::MICROSEC_PER_SEC);
+            \usleep((int) ($timeout * self::MICROSEC_PER_SEC));
         }
     }
 

lib/Producer.php

@@ -14,7 +14,7 @@ final class Producer implements Iterator
     use CallableMaker, Internal\Producer;
 
     /**
-     * @param callable(callable(TValue $value): Promise $emit): \Generator $producer
+     * @param callable(callable(TValue):Promise):\Generator $producer
      *
      * @throws \Error Thrown if the callable does not return a Generator.
      */

lib/TimeoutException.php

@@ -10,7 +10,7 @@ namespace Amp;
 class TimeoutException extends \Exception
 {
     /**
-     * @param string|null $message Exception message.
+     * @param string $message Exception message.
      */
     public function __construct(string $message = "Operation timed out")
     {