Add support for g6f.2xlarge

[jnioche]

The g6f.2xlarge is an Amazon Web Services (AWS) EC2 GPU instance featuring 8 vCPUs, 32 GiB of memory, a fractional NVIDIA L4 GPU (0.25 share), and up to 10 Gbps of network bandwidth,

[jnioche]

These have fractions of a GPU, need to check that Boavizta can handle a float

[jnioche]

See Boavizta/boaviztapi#563