vala: update to 0.38.3.

Vala 0.38.3
===========
* Various bug fixes:
  - codegen: Prioritize "array_length=true" over "array_null_terminated=true"
    [#788775]
  - codegen: Avoid possible conflicts with internal property/signal defines
    [#788964]

* Bindings:
  - gio-2.0: Expose g_task_get_source_object as Task.get_unowned_source_object
  - gstreamer-1.0: Update from 1.13+ git master
  - gtk+-4.0: Update to 3.92.1
  - libxml-2.0: Add DTD methods [#789442]

Vala 0.38.2
===========
* Various bindings updates:
  - gstreamer-1.0,gtk+-3.0,gtk+-4.0: Update from git master
  - gnutls: Fix free_function ccode-attribute of Certificate [#788181]

(wiz)