[gimp] app: remove useless code.

[Jehan <jehanp src gnome org>]

commit d9840893c06653a4ea1c1f8edf6d0c619013c998
Author: Jehan <jehan girinstud io>
Date:   Mon Feb 22 00:10:17 2021 +0100

    app: remove useless code.
    
    Fixes warning brought by my commit 015f49467d:
    > warning: variable ‘max_position’ set but not used [-Wunused-but-set-variable]

 app/tools/gimpguidetool.c | 6 ------
 1 file changed, 6 deletions(-)
---
diff --git a/app/tools/gimpguidetool.c b/app/tools/gimpguidetool.c
index 5e1db2ee19..e8676d4bfa 100644
--- a/app/tools/gimpguidetool.c
+++ b/app/tools/gimpguidetool.c
@@ -167,12 +167,6 @@ gimp_guide_tool_button_release (GimpTool              *tool,
       for (i = 0; i < guide_tool->n_guides; i++)
         {
           GimpGuideToolGuide *guide = &guide_tool->guides[i];
-          gint                max_position;
-
-          if (guide->orientation == GIMP_ORIENTATION_HORIZONTAL)
-            max_position = gimp_image_get_height (image);
-          else
-            max_position = gimp_image_get_width (image);
 
           n_non_custom_guides += ! guide->custom;