minor #37833 Added missing router config (dragosprotung)

This PR was merged into the 5.1 branch.

Discussion
----------

Added missing router config

    | Q             | A
    | ------------- | ---
    | Branch?       | 5.1
    | Bug fix?      | yes
    | New feature?  | no
    | Deprecations? | no
    | Tickets       | N/A
    | License       | MIT
    | Doc PR        | N/A

Commits
-------

a3bfb7d204 Added missing router config

Author: fabpot

Resources/config/schema/symfony-1.0.xsd

@@ -95,6 +95,7 @@
         <xsd:attribute name="https-port" type="xsd:string" />
         <xsd:attribute name="strict-requirements" type="xsd:string" />
         <xsd:attribute name="utf8" type="xsd:boolean" />
+        <xsd:attribute name="default-uri" type="xsd:string" />
     </xsd:complexType>
 
     <xsd:complexType name="session">