Fix an error in Loader code documentation

That's not $this->load_vars(), but $this->load->vars()
diff --git a/system/core/Loader.php b/system/core/Loader.php
index 94739c7..d51ee0b 100644
--- a/system/core/Loader.php
+++ b/system/core/Loader.php
@@ -820,7 +820,7 @@
 		/*
 		 * Extract and cache variables
 		 *
-		 * You can either set variables using the dedicated $this->load_vars()
+		 * You can either set variables using the dedicated $this->load->vars()
 		 * function or via the second parameter of this function. We'll merge
 		 * the two types and cache them so that views that are embedded within
 		 * other views can have access to these variables.