chore: update Trino benchmark image

[bill-ph]

The scheduled benchmark still pins a Trino image from before PostHog/trino#31, so runs on Duckgres main do not exercise the redundant Parquet index-read optimization.

Update the shared TRINO_IMAGE pin to the PR #31 merge commit, 59184e0c58c2fdbde031f3a08787c926dc4d7f69, with its verified immutable GHCR digest. Both standard and cached Trino scenarios use this image.

Validation:

• Verified the GHCR tag resolves to the pinned digest and includes a Linux ARM64 manifest.
• just test-scenario passed.
• git diff --check passed; focused review found no issues.
• just lint reports six Staticcheck SA4023 diagnostics in unchanged Go files (main.go, cmd/duckgres-controlplane/main.go, and controlplane/control.go).

This updates the benchmark input; it does not establish a performance gain. The benchmark has not been rerun with this pin yet.

[github-actions]

Test Impact Plan

Deterministic summary of how this PR changes tests, CI runners, and coverage-risk signals.

Summary

Area	Added	Changed	Deleted
Test files	0	0	0
E2E/journey files	0	0	0
Workflow files	0	1	0

Signals

• Test cases: +0 / -0
• Assertions: +0 / -0
• Skips or known failures added: 0
• Workflow continue-on-error added: 0
• Workflow path filters added: 0
• Test commands removed from justfile: 0
• E2E/journey retry lines added: 0

Coverage risk: neutral or increased

No coverage-reduction warnings detected.