CI flake: unity-testsuite Docker Hub 502 pulling Unity editor

[clockwork-labs-bot]

Detected manually from a GitHub Actions run requested in #ci-gremlin.

Tests:

• unity-testsuite

Error:
Docker failed while pulling the Unity editor image from Docker Hub:

docker: unknown: failed to copy: httpReadSeeker: failed open: unexpected status from GET request to https://registry-1.docker.io/v2/unityci/editor/blobs/sha256:196ea3960e275155a3d719affa851630a44d3333481958999ad3e66d6e6e7055: 502 Bad Gateway
The process '/usr/bin/docker' failed with exit code 125

Failed job run:

• https://github.com/clockworklabs/SpacetimeDB/actions/runs/27349101052/job/80806362277 (unity-testsuite, merge queue run, commit c0d1c9dac306ceec1477403777a950729cb46a94)