minor #6153 Update filters.rst (alexandre-mace)

This PR was merged into the 4.x branch.

Discussion
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Update filters.rst

Fix call to an undefined method

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ea6471b Update filters.rst

doc/filters.rst

@@ -210,7 +210,7 @@ the ``country`` property of the ``customer``). In those cases, set the
             return $filters
                 // 'country' doesn't exist as a property of 'Order' so it's
                 // defined as 'not mapped' to avoid errors
-                ->add(CustomerCountryFilter::new('country')->mapped(false))
+                ->add(CustomerCountryFilter::new('country')->setFormTypeOption('mapped', false))
             ;
         }
     }