stop testing the underlying library

On ubuntu mathines, this still returns PM even in the netherland's locale for both zend and us. I think we shouldn't test it.

hphp/test/slow/ext_date/1776.php

@@ -1,3 +1,9 @@
 <?php
 
- error_reporting(0);var_dump(idate('@@'));var_dump(idate('@'));var_dump(date(''));var_dump(date('@'));var_dump(strftime(''));setlocale(LC_ALL, 'nl_NL');var_dump(strftime('%p'));
+error_reporting(0);
+var_dump(idate('@@'));
+var_dump(idate('@'));
+var_dump(date(''));
+var_dump(date('@'));
+var_dump(strftime(''));
+var_dump(strftime('%p', 1234567890));

hphp/test/slow/ext_date/1776.php.expect

@@ -3,4 +3,4 @@ bool(false)
 string(0) ""
 string(1) "@"
 bool(false)
-bool(false)
+string(2) "PM"