cos-gpu-installer: release v2.6.6 with reverted firmware change

BUG=b/497002114
TEST=pull container from cos staging, push to dev project and install on a VM:
sudo docker run --rm -it --privileged   -e NVIDIA_INSTALL_DIR_HOST=/home/kubernetes/bin/nvidia   -e NVIDIA_INSTALL_DIR_CONTAINER=/usr/local/nvidia   -e VULKAN_ICD_DIR_HOST=/home/kubernetes/bin/nvidia/vulkan/icd.d   -e VULKAN_ICD_DIR_CONTAINER=/etc/vulkan/icd.d   -e ROOT_MOUNT_DIR=/root   -e COS_TOOLS_DIR_HOST=/var/lib/cos-tools   -e COS_TOOLS_DIR_CONTAINER=/build/cos-tools   -v /dev:/dev   -v /home/kubernetes/bin/nvidia:/usr/local/nvidia   -v /home/kubernetes/bin/nvidia/vulkan/icd.d:/etc/vulkan/icd.d   -v /:/root   -v /var/lib/cos-tools:/build/cos-tools us.gcr.io/<dev-project>/cos-gpu-installer:staging
RELEASE_NOTE=None

Change-Id: Ice46329ca88d6f8a9db5d6b378d9059b678865dd
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/141743
Tested-by: Miri Amarilio <mirilio@google.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Cloud-Build: Miri Amarilio <mirilio@google.com>