[gimp-help] Remove dead link to jimmac's old icon theme.

[Jacob Boerema <jboerema src gnome org>]

commit ced77a4ad1a49dccdbe964e21993fbd48fd6b2a5
Author: Jacob Boerema <jgboerema gmail com>
Date:   Thu May 20 11:57:20 2021 -0400

    Remove dead link to jimmac's old icon theme.

 src/appendix/history-24.xml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/appendix/history-24.xml b/src/appendix/history-24.xml
index 0796fb1f7..f3b70b2f4 100644
--- a/src/appendix/history-24.xml
+++ b/src/appendix/history-24.xml
@@ -38,7 +38,7 @@
         <para>
           For artists preferring more desaturated color theme for their icons
           is an alternative icon theme available for download
-          <xref linkend="bibliography-online-jimmac01"/>.
+          (download not available anymore).
         </para>
       </listitem>
     </varlistentry>