minor #7955 Fixed the parse() method in the ExpressionLanguage AST examples (javiereguiluz)

This PR was submitted for the 3.3 branch but it was merged into the 3.2 branch instead (closes #7955).

Discussion
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Fixed the parse() method in the ExpressionLanguage AST examples

This fixes #7943.

Commits
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551624d Fixed the parse() method in the ExpressionLanguage AST examples

Author: xabbuh

components/expression_language/ast.rst

@@ -21,7 +21,7 @@ method after parsing any expression to get its AST::
     use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
 
     $ast = (new ExpressionLanguage())
-        ->parse('1 + 2')
+        ->parse('1 + 2', array())
         ->getNodes()
     ;
 
@@ -41,7 +41,7 @@ method to turn the AST into an array::
     // ...
 
     $astAsArray = (new ExpressionLanguage())
-        ->parse('1 + 2')
+        ->parse('1 + 2', array())
         ->getNodes()
         ->toArray()
     ;