Fix expectation in mixed_property_inheritance_error7.phpt

Author: TimWolla

Zend/tests/type_declarations/mixed/inheritance/mixed_property_inheritance_error7.phpt

@@ -15,4 +15,4 @@ class Bar extends Foo
 
 ?>
 --EXPECTF--
-Fatal error: Type of Bar::$property1 be omitted to match the parent definition in class Foo in %s on line %d
+Fatal error: Type of Bar::$property1 must be omitted to match the parent definition in class Foo in %s on line %d