cmd/stbench: rm -r cmd/stbench (#6131)
cmd/stbench: rm -r cmd/stbench (#6131)

This is apparently an old benchmarking tool. I'd forgotten about it.
Since 67b8ef1f3ef419c5e9d561aa6dd88e7e1eaf9901 the build script tries to
build all binaries explicitly by default, and this fails on Windows as
this tool doesn't build on Windows.

Kill it with fire.
AudriusButkevicius/syncthing,syncthing/syncthing,syncthing/syncthing,AudriusButkevicius/syncthing,syncthing/syncthing,imsodin/syncthing,imsodin/syncthing,imsodin/syncthing,AudriusButkevicius/syncthing,wweich/syncthing,syncthing/syncthing,AudriusButkevicius/syncthing,wweich/syncthing,syncthing/syncthing,imsodin/syncthing,imsodin/syncthing,wweich/syncthing,syncthing/syncthing,wweich/syncthing