Fix the case of the "@inheritDoc" tag

According to the official documentation [1] the correct way of writing
the "inheritDoc" tag is with the uppercase "D".

[1]: https://docs.phpdoc.org/guides/inheritance.html

Signed-off-by: Henrique Moody <henriquemoody@gmail.com>

library/Exceptions/ExecutableException.php

@@ -20,7 +20,7 @@ namespace Respect\Validation\Exceptions;
 final class ExecutableException extends ValidationException
 {
     /**
-     * {@inheritdoc}
+     * {@inheritDoc}
      */
     public static $defaultTemplates = [
         self::MODE_DEFAULT => [