Remove superfluous checks for PNG support

PNG support is required to build ext/gd, so there's no need to check
for it in the tests.

Author: cmb69

ext/gd/tests/bug72604.phpt

@@ -3,7 +3,6 @@ Bug #72604 (imagearc() ignores thickness for full arcs)
 --SKIPIF--
 <?php
 if (!extension_loaded('gd')) die('skip requires ext/gd');
-if (!(imagetypes() & IMG_PNG)) die('skip requires PNG support');
 ?>
 --FILE--
 <?php

ext/gd/tests/imagecopyresampled_basic.phpt

@@ -3,7 +3,6 @@ imagecopyresampled()
 --SKIPIF--
 <?php 
 	if (!function_exists('imagecopyresampled')) die('skip imagecopyresampled() not available'); 
-	if (!(imagetype() & IMG_PNG)) die('skip PNG Support is not enabled');
 ?>
 --FILE--
 <?php

ext/gd/tests/imagedashedline_basic.phpt

@@ -3,7 +3,6 @@ imagedashedline()
 --SKIPIF--
 <?php 
 	if (!function_exists('imagedashedline')) die('skip imagedashedline() not available'); 
-	if (!(imagetype() & IMG_PNG)) die('skip PNG Support is not enabled');
 ?>
 --FILE--
 <?php

ext/gd/tests/imagefilledpolygon_basic.phpt

@@ -3,7 +3,6 @@ imagefilledpolygon()
 --SKIPIF--
 <?php 
 	if (!function_exists('imagefilledpolygon')) die('skip imagefilledpolygon() not available'); 
-	if (!(imagetype() & IMG_PNG)) die('skip PNG Support is not enabled');
 ?>
 --FILE--
 <?php