Log Message:
vala: update to 0.56.1.

Vala 0.56.1
===========
 * Various improvements and bug fixes:
  - vala: Improve accessibility check inside member initializer [#1300]
  - vala: Don't allow nullable enum value as real GObject property [#1074]
  - valadoc: Include path to doclet in error message
  - manual: Update from wiki.gnome.org

 * Bindings:
  - gtk4: Fix GLib.Value parameter in ContentProvider.get_value()
  - gtk4: Split out gtk4-wayland and gtk4-x11 into separate bindings [#1308]
  - gstreamer: Update from 1.21+ git main
  - vapi: Update GIR-based bindings