build: meson: Add trailing commas

Add missing trailing commas that avoids getting noise when another
file/parameter is added and eases reviewing changes[0].

[0] https://gitlab.gnome.org/GNOME/dconf/merge_requests/11#note_291585

vapi/meson.build

@@ -2,20 +2,20 @@ gnome.generate_vapi(
   libnm_name,
   sources: libnm_gir[0],
   packages: 'gio-2.0',
-  install: true
+  install: true,
 )
 
 if enable_libnm_glib
   packages = [
     'dbus-glib-1',
-    'gio-2.0'
+    'gio-2.0',
   ]
 
   libnm_util_vapi = gnome.generate_vapi(
     libnm_util_name,
     sources: libnm_util_gir[0],
     packages: packages,
-    install: true
+    install: true,
   )
 
   gnome.generate_vapi(
@@ -23,6 +23,6 @@ if enable_libnm_glib
     sources: libnm_glib_gir[0],
     packages: packages + [libnm_util_vapi],
     gir_dirs: [join_paths(meson.current_build_dir(), '..', 'libnm-util')],
-    install: true
+    install: true,
   )
 endif