removed wrong routing xsd statement `mixed="true"`
removed wrong routing xsd statement `mixed="true"`

mixed="true" means that the element could contain both text and other elements, e.g.
`<requirement key="_locale">text <subelement /></requirement>`
But this wrong and such a definition would not even validate against the scheme as the xsd does not define which elements would be expected inside.
tecnocat/routing,symfony/Routing