Fixed #1892: Rename 'confusing' option to something more descriptive

Author: derickr

downloads.php

@@ -95,7 +95,7 @@ function option(string $value, string $desc, $attributes = []): string
     '8.4' => 'version 8.4',
     '8.3' => 'version 8.3',
     '8.2' => 'version 8.2',
-    'default' => 'OS default version',
+    'default' => 'default PHP version for OS',
 ];