doc: utf32toString byte length validation documentation

[Copilot]

TypeScript definitions incorrectly documented UTF-32 decoding functions as throwing on "non-even byte length" when they actually validate byteLength % 4 !== 0.

Changes

• utf32.d.ts: Updated documentation comments (lines 61, 80) to state "Throws on byte length not a multiple of 4"

UTF-32 uses 4 bytes per codepoint. The implementation in utf32.js correctly validates multiples of 4, but the type definitions were left with incorrect documentation after a previous fix to the error messages.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Review the codebase and identify mistakes</issue_title>
<issue_description>Ignore tests/wpt and other vendored tests

Note: wif using synchronous path for async implementation is not an issue, it's done for perf, as underlying method is always sync (again, for perf).</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Review the codebase and identify mistakes #43

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