roachtest: use 'master' tag for tpc-e docker images

[srosenberg]

In [1], [2], we moved tpc-e docker images from the Docker Hub to a publicly accessible Google Container Registry (under https://us-east1-docker.pkg.dev/v2/crl-ci-images). Consequently, most recent changes to tpc-e are now tagged as 'master'. (This happens as part of the docker GH action upon merging a PR into master.)

[1] https://github.com/cockroachlabs/tpc-e/pull/71
[2] #117691

Epic: none

Release note: None

[cockroach-teamcity]

This change is 

[srosenberg]

TFTR!

bors r=rail

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from 3642993 to blathers/backport-release-23.1-117795: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 23.1.x failed. See errors above.

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error creating merge commit from 3642993 to blathers/backport-release-23.2-117795: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 23.2.x failed. See errors above.

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