desktop: change gimp20 to gimp30 for gettext

The real used value for gettext_package is
already changed in meson.build

README.i18n

@@ -19,13 +19,13 @@ GIMP is different
  not one catalog but many. For a full translation of GIMP's UI, you
  will have to add translations for the following catalogs:
 
-   po/gimp20.po                                       --  the core
+   po/gimp30.pot                                      --  the core
-   po-libgimp/gimp20-libgimp.pot                      --  the libgimp library
+   po-libgimp/gimp30-libgimp.pot                      --  the libgimp library
-   po-plugins/gimp20-std-plugins.pot                  --  the C plug-ins
+   po-plugins/gimp30-std-plugins.pot                  --  the C plug-ins
-   po-python/gimp20-python.pot                        --  the pygimp plug-ins
+   po-python/gimp30-python.pot                        --  the pygimp plug-ins
-   po-script-fu/gimp20-script-fu.pot                  --  the script-fu scripts
+   po-script-fu/gimp30-script-fu.pot                  --  the script-fu scripts
-   po-tips/gimp20-tips.pot                            --  the startup tips
+   po-tips/gimp30-tips.pot                            --  the startup tips
-   po-windows-installer/gimp20-windows-installer.pot  --  the windows installer
+   po-windows-installer/gimp30-windows-installer.pot  --  the windows installer
 
  If you are looking for the translations of gimp-perl, please note that
  gimp-perl has been moved into it's own git module called

build/linux/appimage/patches/0001-desktop-po-Use-reverse-DNS-naming.patch

@@ -1,6 +1,6 @@
-From dc8762b7a11794a3481eced7ff0eaf9202b7799e Mon Sep 17 00:00:00 2001
+From e3c70a67c9f03a3a5af44b1dcf87a3cda4f4443b Mon Sep 17 00:00:00 2001
 From: Bruno Lopes <brunolopesdsilv@outlook.com>
-Date: Sat, 30 Mar 2024 13:53:37 -0300
+Date: Thu, 29 Aug 2024 00:34:06 +0200
 Subject: [PATCH] desktop, po: Use reverse DNS naming
 
 ---
@@ -24,12 +24,12 @@ index bee2e93c48..a517e351ab 100644
  desktop_conf = configuration_data()
  desktop_conf.set('GIMP_COMMAND',      gimp_command)
 diff --git a/desktop/org.gimp.GIMP.appdata.xml.in.in b/desktop/org.gimp.GIMP.appdata.xml.in.in
-index fbc01608bf..e934469013 100644
+index e1dcfa7fdc..41a51e1b68 100644
 --- a/desktop/org.gimp.GIMP.appdata.xml.in.in
 +++ b/desktop/org.gimp.GIMP.appdata.xml.in.in
 @@ -65,12 +65,12 @@
    </kudos>
-   <translation type="gettext">gimp20</translation>
+   <translation type="gettext">gimp30</translation>
  
 -  <launchable type="desktop-id">gimp.desktop</launchable>
 +  <launchable type="desktop-id">org.gimp.GIMP.desktop</launchable>
@@ -117,7 +117,7 @@ index 0ebe7fa7e0..046e737fca 100644
    if (pixbuf)
      icons = g_list_prepend (icons, pixbuf);
 diff --git a/po/POTFILES.in b/po/POTFILES.in
-index bb40043cde..130728ca42 100644
+index bc577b54a4..11bb18e8c1 100644
 --- a/po/POTFILES.in
 +++ b/po/POTFILES.in
 @@ -2,7 +2,7 @@
@@ -143,5 +143,5 @@ index 7e957d8dd4..00ec4d8961 100644
  libgimp
  libgimpbase
 -- 
-2.44.0.windows.1
+2.43.0
 

desktop/org.gimp.GIMP.appdata.xml.in.in

@@ -63,7 +63,7 @@
     <kudo>ModernToolkit</kudo>
     <kudo>UserDocs</kudo>
   </kudos>
-  <translation type="gettext">gimp20</translation>
+  <translation type="gettext">gimp30</translation>
 
   <launchable type="desktop-id">gimp.desktop</launchable>
   <provides>