Update cos-gpu-installer to v2.0.26

Update for K80 driver GPU fallback behavior.

RELEASE_NOTE=Updated cos-gpu-installer to v2.0.26. This resolves the
compatibility issue with K80 GPU devices. When an incompatible driver
version (R510+) is chosen in an instance with K80 GPU, the installer
will automatically fall back to an available R470 driver version.

Change-Id: I44b4b245d2aa317f3b8e951ea4c2dcec42590708
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/36649
Reviewed-by: Arnav Kansal <rnv@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
2 files changed