Improve link to use keyword

https://bugs.php.net/80635

Author: vrana

appendices/reserved.xml

@@ -250,7 +250,7 @@
       </row>
       <row>
        <entry>
-        <link linkend="language.namespaces">use</link>
+        <link linkend="language.namespaces.importing">use</link>
        </entry>
        <entry>
         <link linkend="language.oop5.properties">var</link>