Fix: Add missing 'new' keyword in rate limit error throwing

[WhiteKiwi]

Summary

Although both expressions work in JavaScript, the standard practice is to use new when instantiating error objects to ensure proper behavior and readability. This change, while not affecting functionality, aligns our code with conventional JavaScript practices.

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[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @WhiteKiwi to sign the Salesforce Inc. Contributor License Agreement.

[seratch]

Thanks for sending this PR! This improves the code consistency