downloads: update the link to the macos section

Author: davvid

_includes/download-box.html

@@ -36,7 +36,7 @@
             >Windows</a>
     </td>
     <td width="33%">
-        <a href="https://github.com/git-cola/git-cola#mac-os-x"
+        <a href="https://github.com/git-cola/git-cola?tab=readme-ov-file#macos"
             >Mac OSX</a>
     </td>
     <td width="33%">