check: fix dash_mpdparser_check_mpd_client_set_methods test.

Setting guint64 valist properties without type specifier fails
on 32bit archs.

Part-of: <gstreamer/gst-plugins-bad!2162>
29 jobs for !2162 with backport-mr-2161-into-1.18-fix_dash_mpd_test in 44 minutes and 15 seconds (queued for 5 seconds)
merge request