Applied a new flag to jxl-perfhistory

[zond]

The comment itself won't be real Markdown until the main branch has the right code in the workflow, so the example comment in this PR still has the triple single quotes that make it render as quoted code.

[github-actions]

Benchmark @ c437402

MULTI-FILE BENCHMARK RESULTS (4 files)
CPU architecture: x86_64
WARNING: System appears noisy: high system load (2.16). Results may be unreliable.
Statistics:
Confidence: 99.0%
Max relative error: 3.0%

**Comparing:** [135c38d6](https://github.com/libjxl/jxl-rs/commit/135c38d62e234453cfd7aef4edbf7f2b704c763b) (Base) vs [b7c0cc1d](https://github.com/libjxl/jxl-rs/commit/b7c0cc1db28c8f330f93aca23ffc5d43fe28dbec) (PR)

| File | Base (MP/s) | PR (MP/s) | Δ% |
|:-----|------------:|----------:|---:|
| bike.jxl | 23.854 | 24.053 | +0.83% ±0.7% |
| green_queen_modular_e3.jxl | 8.165 | 8.151 | -0.17% ±0.5% |
| green_queen_vardct_e3.jxl | 20.508 | 20.474 | -0.17% ±0.5% |
| sunset_logo.jxl | 2.229 | 2.232 | +0.14% ±0.9% |