The actions/customer/external/updated/sender.js sendData method does not return a response

Description

The actions/customer/external/updated/sender.js sendData method returns a response that can be checked by the actions/customer/external/updated/index.js main function to check the success or failure of the invocation.

    logger.debug(`Start sending data: ${JSON.stringify(transformed)}`)
    const result = await sendData(params, transformed, preProcessed)
    if (!result.success) {
      logger.error(`Send data failed: ${result.message}`)
      return actionErrorResponse(result.statusCode, result.message)
    }

Motivation and Context

This PR fixes a bug in the starter-kit that causes an error response when processing a be-observer.customer_update event

How Has This Been Tested?

The issue has been tested while working on a project based on the starter kit by sending a `be-observer.customer_update event and checking that it is successfully processed after deploying the change.

Screenshots (if appropriate):

N/A

Types of changes

[x] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

[x] I have signed the Adobe Open Source CLA.
[x] My code follows the code style of this project.
[ ] My change requires a change to the documentation.
[ ] I have updated the documentation accordingly.
[x] I have read the CONTRIBUTING document.
[ ] I have added tests to cover my changes.
[x] All new and existing tests passed.

adobe / commerce-integration-starter-kit