MDL-43402 let's try to remove @ silencing from gzip related code

If anything goes wrong on multiple production sites we can just
revert this commit, that is why it is separete from the rest
of zlib stuff.

lib/setup.php

@@ -985,9 +985,9 @@ if (PHPUNIT_TEST) {
 
 // // try to detect IE6 and prevent gzip because it is extremely buggy browser
 if (!empty($_SERVER['HTTP_USER_AGENT']) and strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE 6') !== false) {
-    @ini_set('zlib.output_compression', 'Off');
+    ini_set('zlib.output_compression', 'Off');
     if (function_exists('apache_setenv')) {
-        @apache_setenv('no-gzip', 1);
+        apache_setenv('no-gzip', 1);
     }
 }