Update float runner to fix password issue

Due to some upstream changes in vmine this has caused the float run site.yml part of the float-run-validation stage in CI to fail. The vmine VM creation works, the init-credentials works, but then when the float run site.yml happenes, its complaining about a SSH password being requested. The vmine upstream did a bunch of simplifications last week, (eg. getting rid of of autopkgtest-build-qemu and just using vmdb2 directly now), but as a result the default 'vagrant-insecure' ssh key was dropped.

If the latest floatup.py from https://git.autistici.org/ai3/docker/float-runner is used, it will autogenerate a new ssh key on the fly for you, which would not require any other changes. That could either be part of a general upstream float update, or that script pulled in independently in the CI before its run.