Fix unused argument in sprintf expression in CacheControl

Not clear on the impact, this was detected via static analysis.

Author: TysonAndre

src/Header/CacheControl.php

@@ -39,7 +39,7 @@ public static function fromString($headerLine)
         // check to ensure proper header type for this factory
         if (strtolower($name) !== 'cache-control') {
             throw new Exception\InvalidArgumentException(sprintf(
-                'Invalid header line for Cache-Control string: ""',
+                'Invalid header line for Cache-Control string: "%s"',
                 $name
             ));
         }