Track taffy replaced-element fixes stack (taffy#1156–#1158)

[nicoburns]

Summary

Bumps the taffy git dependency rev to d66b6e6c, the HEAD of the taffy replaced-element PR stack:

1. Add image (replaced element) support to the test generator taffy#1156 — image (replaced element) support in the test generator
2. Fix transferred-size computation for replaced leaf nodes taffy#1157 — replaced leaf transferred-size fix (intrinsic aspect ratio applied when only one dimension is specified)
3. Default replaced grid items to start alignment per css-align-3 taffy#1158 — replaced grid items default to start alignment per css-align-3 (fixes stretch and auto-track sizing of images in grid)

Draft while the stack is in review; I'll bump the rev as the stack updates and retarget to a taffy release once it lands.

Link to Devin session: https://dioxus.staging.devinenterprise.com/sessions/e168cf7cbcd34c939e1cc5d4e000836b
Open in Devin Desktop: https://dioxus.staging.devinenterprise.com/desktop/session/e168cf7cbcd34c939e1cc5d4e000836b?variant=devin-insiders
Requested by: @nicoburns

WPT results

No changes in test results compared to main.

_{Generated by the WPT workflow.}

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