[ci] Fix tests requirements

Author: nicolas-grekas

Tests/Extension/Core/DataTransformer/DateTimeToStringTransformerTest.php

@@ -122,13 +122,10 @@ public function testTransformExpectsDateTime()
 
     /**
      * @dataProvider dataProvider
+     * @requires PHP 5.3.7
      */
     public function testReverseTransformUsingPipe($format, $input, $output)
     {
-        if (PHP_VERSION_ID < 50307) {
-            $this->markTestSkipped('Pipe usage requires PHP 5.3.7 or newer.');
-        }
-
         $reverseTransformer = new DateTimeToStringTransformer('UTC', 'UTC', $format, true);
 
         $output = new \DateTime($output);

Tests/Extension/Core/EventListener/TrimListenerTest.php

@@ -42,13 +42,10 @@ public function testTrimSkipNonStrings()
 
     /**
      * @dataProvider spaceProvider
+     * @requires extension mbstring
      */
     public function testTrimUtf8Separators($hex)
     {
-        if (!function_exists('mb_convert_encoding')) {
-            $this->markTestSkipped('The "mb_convert_encoding" function is not available');
-        }
-
         // Convert hexadecimal representation into binary
         // H: hex string, high nibble first (UCS-2BE)
         // *: repeat until end of string