fix: overrides sandbox attr on iframes

[AutoSponge]

Removes and re-injects sandboxed iframes without the sandbox attribute prior to injecting axe.

Paired with: @michael-siek

Closes issue: dequelabs/attest-node-suite#246 dequelabs/attest-node-suite#332

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[AutoSponge]

Make sure this goes to "docs" after merge.