CI: scratch: fix not working on older mingw versions
The current default is r32g32b32a32 but it requires special support which is not available on all GPUs, so it is not a very convenient default.
Instead of changing the default making it different from RTV resoures, the format is required to always be explicit for UAVs.
The exceptions are counter_buffer and buffers with "stride", which don't require a format because it is already implied.