tests: explicitly require libsoup 2.x

As if libsoup3 is installed together with libsoup2, libsoup3 is selected
which makes test fails.

Signed-off-by: Mateusz Gozdek <mgozdekof@gmail.com>

tests/object__initialization.js

@@ -5,7 +5,7 @@
 
 const gi = require('../lib/')
 const Gtk = gi.require('Gtk', '3.0')
-const Soup = gi.require('Soup')
+const Soup = gi.require('Soup', '2.4')
 const { describe, it, mustThrow, expect, assert } = require('./__common__.js')
 
 Gtk.init()