meson/gio: Increase timeout for the codegen python tests

It's adding more stuff, let's ensure it wont timeout for no reason in
some platforms.

As per this mark also it as 'slow'

gio/tests/meson.build

@@ -172,7 +172,8 @@ python_tests = {
   # FIXME: https://gitlab.gnome.org/GNOME/glib/-/issues/2764
   'codegen.py' : {
     'can_fail' : host_system == 'freebsd',
-    'suite': ['gdbus-codegen'],
+    'suite': ['gdbus-codegen', 'slow'],
+    'timeout': 90,
   },
 }
 
@@ -1068,6 +1069,7 @@ foreach test_name, extra_args : python_tests
     depends: depends,
     args: ['-B', files(test_name)],
     env: test_env,
+    timeout: extra_args.get('timeout'),
     suite: suite,
   )