[gimp-help] Add help-id for desaturate/color-to-gray.xml

[Jacob Boerema <jboerema src gnome org>]

commit 07ccbd5f7dbec42b3fd9cef74450c5d1258646d1
Author: Jacob Boerema <jgboerema gmail com>
Date:   Thu May 20 13:04:14 2021 -0400

    Add help-id for desaturate/color-to-gray.xml

 src/menus/colors/desaturate/color-to-gray.xml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/menus/colors/desaturate/color-to-gray.xml b/src/menus/colors/desaturate/color-to-gray.xml
index af5db79cc..fdb1ac2be 100644
--- a/src/menus/colors/desaturate/color-to-gray.xml
+++ b/src/menus/colors/desaturate/color-to-gray.xml
@@ -5,7 +5,7 @@
   2018-06-08 j.h Created empty
 -->
 
-<sect2> <!-- id not found -->
+<sect2 id="gimp-filter-c2g">
   <title>Color to Gray</title>
   <para>TODO</para>
 </sect2>
\ No newline at end of file