Revert "Use random_bytes when available (#487)"

This reverts commit fa0ac8cd2336052286cd3556889449660e4d9c83.

backend/garbage.php

@@ -53,11 +53,7 @@ function sendHeaders()
 $chunks = getChunkCount();
 
 // Generate data
-if (function_exists('random_bytes')) {
-    $data = random_bytes(1048576);
-} else {
-    $data = openssl_random_pseudo_bytes(1048576);
-}
+$data = openssl_random_pseudo_bytes(1048576);
 
 // Deliver chunks of 1048576 bytes
 sendHeaders();