Error calling CognitoIdentityProviderClient methods: "Failed to fetch"

When sending commands through the `CognitoIdentityProviderClient` we're getting a `Failed to fetch` error. In our case it was with `ListUserPoolsCommand`, but it seems to happen with more of them.

This was found in a **Lambda** function that was running fine on **LLRT 0.8.1** and started failing when upgrading to **LLRT 0.9.0**, so this looks like a regression. There's a script attached to reproduce the bug.

Tell me if you need anything else :)

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SDK Version: `@aws-sdk/client-cognito-identity-provider ^3.799.0`
LLRT Version: `0.9.0`

[bug-repro.zip](https://github.com/user-attachments/files/32014482/bug-repro.zip)

Start with the attached bug-repro.zip and its CognitoIdentityProviderClient invocation, focusing on ListUserPoolsCommand. Compare the behavior on LLRT 0.9.0 with 0.8.1 using the stated AWS SDK version. Done means the reproduction no longer returns "Failed to fetch" on the affected Cognito methods.

Written by the indexing model from the issue text.