Update SonataAdminBundle.de.xliff

Add translation for `btn_advanced_filters`.

Resources/translations/SonataAdminBundle.de.xliff

@@ -36,7 +36,7 @@
             </trans-unit>
             <trans-unit id="btn_advanced_filters">
                 <source>btn_advanced_filters</source>
-                <target>btn_advanced_filters</target>
+                <target>Erweiterte Filter</target>
             </trans-unit>
             <trans-unit id="btn_update">
                 <source>btn_update</source>