Update valid-url.md

Author: milwad-dev

docs/1.x/valid-url.md

@@ -1,6 +1,6 @@
 ## ValidUrl
 
-If you want to validate url, you can use `ValidUrl` rule:
+If you want to validate URL, you can use the `ValidUrl` rule:
 
 ```php
 use Milwad\LaravelValidate\Rules\ValidUrl;