Revert "Update cos-gpu-installer to version v20200701"
Revert "Update cos-gpu-installer to version v20200701"

This reverts commit 267abc750b8039ec5de494d5d8b1fe12aca53bf3.

This change is causing GPU tests to fail.

GoogleCloudPlatform/cos-customizer,GoogleCloudPlatform/cos-customizer