Fix typo in config.php

Looks like a typo of "vary" instead of "wary", and "aware" sounds better.

config.php-dist

@@ -109,7 +109,7 @@
 	// ***********************************
 
 	define('ENABLE_REGISTRATION', false);
-	// Allow users to register themselves. Please be vary that allowing
+	// Allow users to register themselves. Please be aware that allowing
 	// random people to access your tt-rss installation is a security risk
 	// and potentially might lead to data loss or server exploit. Disabled
 	// by default.