[gegl] brightness-contrast: mark string containing % as no-c-format

[Øyvind "pippin" Kolås <ok src gnome org>]

commit a7e60d55e59351a87b04eeee77d6b95b77ffba84
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Feb 13 15:44:38 2019 +0100

    brightness-contrast: mark string containing % as no-c-format
    
    Hoping that this silences xgettext for issue #128.

 operations/common/brightness-contrast.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/operations/common/brightness-contrast.c b/operations/common/brightness-contrast.c
index b612686b5..03528744f 100644
--- a/operations/common/brightness-contrast.c
+++ b/operations/common/brightness-contrast.c
@@ -159,6 +159,8 @@ gegl_op_class_init (GeglOpClass *klass)
       "title",      _("Brightness Contrast"),
       "categories", "color",
       "reference-hash", "a60848d705029cad1cb89e44feb7f56e",
+
+      /* xgettext:no-c-format */
       "description", _("Changes the light level and contrast. This operation operates in linear light, 
'contrast' is a scale factor around 50% gray, and 'brightness' a constant offset to apply after contrast 
scaling."),
       "cl-source"  , brightness_contrast_cl_source,
       "reference-composition", composition,