Drop highlight from the gtk4-demo flatpak

Having it in there requires us to add boost and lua,
which makes it significantly harder to build the
thing.

build-aux/flatpak/org.gtk.Demo4.json

@@ -93,77 +93,6 @@
                 }
             ]
         },
-        {
-            "name": "boost",
-            "buildsystem": "simple",
-            "build-commands": [
-                "./bootstrap.sh --prefix=/app --with-libraries=date_time,filesystem,iostreams,locale,regex,system,thread,python,program_options,test,serialization",
-                "./b2 --build-type=minimal link=shared -j $FLATPAK_BUILDER_N_JOBS",
-                "./b2 --build-type=minimal link=shared install"
-             ],
-             "sources": [
-                 {
-                     "type": "archive",
-                     "url": "https://boostorg.jfrog.io/artifactory/main/release/1.69.0/source/boost_1_69_0.tar.bz2",
-                     "sha256": "8f32d4617390d1c2d16f26a27ab60d97807b35440d45891fa340fc2648b04406"
-                 }
-            ]
-        },
-        {
-            "name": "lua-5.1",
-            "buildsystem": "simple",
-            "build-commands": [
-                "make -j $FLATPAK_BUILDER_N_JOBS CFLAGS=\"$CFLAGS -fPIC -DLUA_USE_LINUX\" linux",
-                "make INSTALL_TOP=$FLATPAK_DEST TO_LIB='liblua.a liblua.so.5.1.5' install",
-                "ln -sf liblua.so.5.1.5 $FLATPAK_DEST/lib/liblua.so",
-                "ln -sf liblua.so.5.1.5 $FLATPAK_DEST/lib/liblua.so.5.1",
-                "install -Dm0644 etc/lua.pc $FLATPAK_DEST/lib/pkgconfig/lua.pc",
-                "ln -sf lua.pc $FLATPAK_DEST/lib/pkgconfig/lua51.pc",
-                "ln -sf lua.pc $FLATPAK_DEST/lib/pkgconfig/lua5.1.pc",
-                "ln -sf lua.pc $FLATPAK_DEST/lib/pkgconfig/lua-5.1.pc"
-            ],
-            "sources": [
-                {
-                    "type": "archive",
-                    "url": "https://www.lua.org/ftp/lua-5.1.5.tar.gz",
-                    "sha256": "2640fc56a795f29d28ef15e13c34a47e223960b0240e8cb0a82d9b0738695333"
-                },
-                {
-                    "type": "patch",
-                    "path": "lua-5.1.5-so.patch"
-                },
-                {
-                    "type": "shell",
-                    "commands": [
-                        "sed -i \"s|/usr/local|$FLATPAK_DEST|\" etc/lua.pc src/luaconf.h"
-                    ]
-                }
-            ],
-            "cleanup": [
-                "*.a",
-                "/bin",
-                "/include",
-                "/lib/pkgconfig",
-                "/man"
-            ]
-        },
-        {
-            "name" : "highlight",
-            "buildsystem" : "simple",
-            "builddir" : true,
-            "build-commands" : [
-                "sed -i -e 's#^PREFIX = /usr#PREFIX = /app#' makefile",
-                "make",
-                "make install"
-            ],
-            "sources" : [
-                {
-                    "type" : "archive",
-                    "url" : "http://www.andre-simon.de/zip/highlight-4.0.tar.bz2",
-                    "sha256" : "f40dcba26e011a2c67df874f4d9b0238c2c6b065163ce8de3d8371b9dfce864d"
-                }
-            ]
-        },
         {
             "name" : "gtk",
             "buildsystem" : "meson",