registration: Don't store 'requires' info as an attribute

We don't need this information at runtime since it only gets checked during
uncached loads of extensions. Also we're trying to shrink the information
we store in the cache (c.f. T187154).

Change-Id: I78d69a944079d346d6b69a4dd1ddb71879f996d0

includes/registration/ExtensionProcessor.php

@@ -115,6 +115,7 @@ class ExtensionProcessor implements Processor {
 	 */
 	protected static $notAttributes = [
 		'callback',
+		'requires',
 		'Hooks',
 		'namespaces',
 		'ResourceFileModulePaths',