package/granite: bump to version 5.4.0

package/granite: bump to version 5.4.0

granite fails to build since bump to vala 0.46.6 in commit
2723ff3333f4f31a06628692bb644552681f8226:

make[3]: Leaving directory '/tmp/instance-0/output-1/build/granite-0.4.1'
[  1%] Generating style-classes.c;Application.c;Drawing/Color.c;Drawing/BufferSurface.c;Drawing/Utilities.c;GtkPatch/AboutDialog.c;Services/Settings.c;Services/Logger.c;Services/Paths.c;Services/System.c;Services/Contractor.c;Services/ContractorProxy.c;Services/IconFactory.c;Services/SimpleCommand.c;Widgets/AlertView.c;Widgets/Avatar.c;Widgets/Utils.c;Widgets/WrapLabel.c;Widgets/AboutDialog.c;Widgets/ModeButton.c;Widgets/DatePicker.c;Widgets/Entries.c;Widgets/TimePicker.c;Widgets/CollapsiblePaned.c;Widgets/StaticNotebook.c;Widgets/DynamicNotebook.c;Widgets/CompositedWindow.c;Widgets/AppMenu.c;Widgets/Welcome.c;Widgets/WelcomeButton.c;Widgets/Toast.c;Widgets/ToolButtonWithMenu.c;Widgets/PopOver.c;Widgets/ContractorView.c;Widgets/ContractorMenu.c;Widgets/DecoratedWindow.c;Widgets/LightWindow.c;Widgets/StatusBar.c;Widgets/SidebarPaned.c;Widgets/StorageBar.c;Widgets/SourceList.c;Widgets/CellRendererExpander.c;Widgets/CellRendererBadge.c;Widgets/ThinPaned.c;Widgets/OverlayBar.c;gr
 anite.vapi;granite.h
make[3]: Entering directory '/tmp/instance-0/output-1/build/granite-0.4.1'
/tmp/instance-0/output-1/build/granite-0.4.1/lib/Application.vala:145.9-145.26: error: Creation method of abstract class cannot be public.
        public Application () {
        ^^^^^^^^^^^^^^^^^^

So bump granite to latest version to include the following commit (that
does not apply cleanly on current version):
https://github.com/elementary/granite/commit/fd26013c84afdeb6300ae2f4a574856753fc2b58

Moreover:
- Switch site to github to get latest release
- Switch to meson-package
- Add gobject-introspection optional dependency

Fixes:
 - http://autobuild.buildroot.org/results/3e2cc89b9bd42824731d0c7b39dd5b5c98e527ee

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>