Update Docker image version in CI configurations

[mukilan]

PR #44493 updated the Dockerfile and also bumped the version of docker image to use in Taskcluster configuration from 0.56 to 0.57. However, 0.57 refers to an exiting image that was published to Docker Hub but never used in the CI configurations.

This PR is to bump the version again so that the changes introduced by #44493 are consumed by the CI configuration.

Also, a new docker image was never published to Docker Hub before #44493 was merged, so that still needs to happen before this PR is merged. Since I don't have permissions to the webplatformtest org on Docker Hub, I'll need someone's help to publish the image before merging the PR.