validate: Properly state that adaptive scenarios are only usable with the gst-validate-transcoding tool in their description.

Submitted by Denis Humeau

Trying to use gst-validate-1.0 the following way:

GST_DEBUG=3 gst-validate-1.0 playbin uri=file:/<my_file> --set-scenario=adaptive_video_size

Result is:
gst-validate-scenario.c:1417:_load_scenario_file:GstValidateScenario@0x52d958 We do not handle action types set-restriction

In practice, the adaptive scenario files are present with the default scenarios, but not usable with devtools 1.4.0.

Is there a devtools version compatible with the use of set-restriction?