replace title_show placeholder with transleted value (#4473)

Resources/translations/SonataAdminBundle.it.xliff

@@ -88,7 +88,7 @@
             </trans-unit>
             <trans-unit id="title_show">
                 <source>title_show</source>
-                <target>title_show</target>
+                <target>Mostra "%name%"</target>
             </trans-unit>
             <trans-unit id="title_dashboard">
                 <source>title_dashboard</source>