Update valid-ulid.md

Author: milwad-dev

docs/1.x/valid-ulid.md

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