Update expression_language.rst

Removing `var_dump`, this make no sens here.

Author: kl3sk

components/expression_language.rst

@@ -123,7 +123,7 @@ This is how you can use these flags::
     $expressionLanguage = new ExpressionLanguage();
 
     // this returns null because the unknown variables and functions are ignored, but don't throw `SyntaxError` exception
-    var_dump($expressionLanguage->lint('unknown_var + unknown_function()', [], Parser::IGNORE_UNKNOWN_VARIABLES | Parser::IGNORE_UNKNOWN_FUNCTIONS));
+    $expressionLanguage->lint('unknown_var + unknown_function()', [], Parser::IGNORE_UNKNOWN_VARIABLES | Parser::IGNORE_UNKNOWN_FUNCTIONS);
 
 .. versionadded:: 7.1