[gimp] Replace C-style comments with JSON keys ignored by Flatpak

[Jehan <jehanp src gnome org>]

commit 54f7f695f340803005c5f82fc6416652d64eb8fb
Author: Ondřej Míchal <harrymichal seznam cz>
Date:   Wed Mar 30 00:50:37 2022 +0300

    Replace C-style comments with JSON keys ignored by Flatpak
    
    JSON does not support comments and their support in Flatpak is possible
    through use of json-glib[0]. This is problematic in fully utilizing
    flatpak-external-data-checker because its JSON writer does not respect
    existing comments. To solve this, make use of Fltpak's specific
    behaviour where a "//" key is explicitely ignored while parsing[1].
    
    [0] flatpak/flatpak-builder#363 (comment)
    [1] 
https://github.com/flatpak/flatpak-builder/blob/0e98b7ae191b81ff66d323ad5dabc2762c5f3f0c/src/builder-utils.c#L1250

 build/flatpak/org.gimp.GIMP-nightly.json | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/build/flatpak/org.gimp.GIMP-nightly.json b/build/flatpak/org.gimp.GIMP-nightly.json
index 1b8724bdf1..d3485f86ed 100644
--- a/build/flatpak/org.gimp.GIMP-nightly.json
+++ b/build/flatpak/org.gimp.GIMP-nightly.json
@@ -355,7 +355,7 @@
             ]
         },
         {
-            /* Copy from shared-modules to avoid submodules on dev repo. */
+            "//": "Copy from shared-modules to avoid submodules on dev repo.",
             "name": "intltool",
             "cleanup": [
                 "*"
@@ -418,13 +418,16 @@
                         "type": "anitya",
                         "project-id": 17096,
                         "stable-only": true,
+                        "versions": {
+                            "<": "2.0.0"
+                        },
                         "url-template": 
"https://github.com/mypaint/mypaint-brushes/releases/download/v$version/mypaint-brushes-$version.tar.xz";
                     }
                 }
             ]
         },
         {
-            /* Shamelessly taken from org.octave.Octave manifest! */
+            "//": "Shamelessly taken from org.octave.Octave manifest!",
             "name": "SuiteSparse",
             "no-autogen": true,
             "make-args": [