docs(library-solidity): resolve variable shadowing in TestAsyncDecrypt example

[qiwihui]

The latestRequestId variable was shadowed, causing myCustomCallback checks to fail.

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[qiwihui]

signed

[aquint-zama]

@cla-bot check

[cla-bot[bot]]

The cla-bot has been summoned, and re-checked this pull request!

[aquint-zama]

Thanks for your PR @qiwihui, could you please rephrase your commit with docs(library-solidity): …?

[qiwihui]

Thanks for your PR @qiwihui, could you please rephrase your commit with docs(library-solidity): …?

Sure. A new commit has been committed and the older one has been revert. Please squash the commits when merging.