Remove useless array casting as CallMap for stream_select is reset.

src/Psalm/Internal/Fork/Pool.php

@@ -365,7 +365,7 @@ class Pool
             }
 
             // For each stream that was ready, read the content.
-            foreach ((array)$needs_read as $file) {
+            foreach ($needs_read as $file) {
                 $buffer = fread($file, 1024);
                 if ($buffer !== false) {
                     $content[(int)$file] .= $buffer;