test(github): generate random filename

[crazy-max]

relates to https://github.com/docker/actions-toolkit/actions/runs/12843876100/job/35816318775#step:10:809

ERROR: read unix @->/run/docker.sock: use of closed network connection
FAIL __tests__/github.test.itg.ts (50.913 s)
  ● uploadArtifact › uploads an artifact

    Failed to CreateArtifact: Received non-retryable error: Failed request: (409) Conflict: an artifact with this name already exists on the workflow run

      at ArtifactHttpClient.<anonymous> (node_modules/@actions/artifact/src/internal/shared/artifact-twirp-client.ts:69:13)
          at Generator.throw (<anonymous>)
      at rejected (node_modules/@actions/artifact/lib/internal/shared/artifact-twirp-client.js:6:65)