[babl] babl: drop a now deprecated const

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

commit d66df63d6355eaf3844af5658a7babe6f9aefa7b
Author: Øyvind Kolås <pippin gimp org>
Date:   Sat Feb 19 18:04:31 2022 +0100

    babl: drop a now deprecated const

 babl/babl-format.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/babl/babl-format.c b/babl/babl-format.c
index 982b851e2..3a8e6c0de 100644
--- a/babl/babl-format.c
+++ b/babl/babl-format.c
@@ -346,7 +346,7 @@ babl_format_new (const void *first_arg,
   int            components = 0;
   BablModel     *model      = NULL;
   const Babl    *space      = babl_space ("sRGB");
-  const char    *doc        = NULL;
+  char          *doc        = NULL;
   BablComponent *component [BABL_MAX_COMPONENTS];
   BablSampling  *sampling  [BABL_MAX_COMPONENTS];
   const BablType*type      [BABL_MAX_COMPONENTS];