[gimp] meson: bump our requirement to meson 0.56.0.

[Jehan <jehanp src gnome org>]

commit dd53de0f0b8fb282d5a1dfd14274d5f4e1312b0d
Author: Jehan <jehan girinstud io>
Date:   Wed Aug 31 00:11:03 2022 +0200

    meson: bump our requirement to meson 0.56.0.
    
    For meson, I want to be particularly careful and not follow the "Debian
    testing" rule as it bit us by the past for babl.
    But this bump is probably OK:
    
    * Debian stable has meson 0.56.2.
    * meson 0.56.0 was released on 2020-10-30.
    * GIMP 2.99 is a dev branch with no end release date yet.
    
    This should also fix this warning at configuration time:
    
    > WARNING: Project specifies a minimum meson_version '>=0.53.0' but uses features which were added in 
newer versions:
    >  * 0.55.0: {'Calling "add_dist_script" with File, CustomTarget, Index of CustomTarget, Executable, or 
ExternalProgram'}
    
    We missed it until now because it was only happening with tarball builds
    where gitversion_h could be a files() object, unlike in git builds.

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 2efdfe3f3b..a1b86ee0a7 100644
--- a/meson.build
+++ b/meson.build
@@ -1,7 +1,7 @@
 project('gimp',
   'c', 'cpp',
   version: '2.99.13',
-  meson_version: '>=0.53.0',
+  meson_version: '>=0.56.0',
   default_options: [
     'cpp_std=gnu++14',
     'buildtype=debugoptimized',