initrd/tests: increase test timeout for "initrd/test-cmdline-reader" with meson

The default timeout of 30 seconds may not be sufficient when running under valgrind
on a busy system.

src/initrd/tests/meson.build

@@ -18,6 +18,7 @@ foreach test_unit : test_units
   test(
     'initrd/' + test_unit,
     test_script,
+    timeout: default_test_timeout,
     args: test_args + [exe.full_path()],
   )
 endforeach