refactor(release): update `release download` cmd to remove `external`

Description

This merge request updates the release download command to remove external field.

The field was deprecated in %15.9 and is bound to be removed in %16.0.

Related Issues

Resolves #1206 (closed).

How has this been tested?

This has been tested manually via the terminal. Please find screenshots below.

Screenshots (if appropriate):

The following is a release with two assets (created using this snippet).

On main, the external release asset link (v5.14.js.map) is not downloaded:

On my branch, all release asset links are downloaded:

Types of changes

• 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)
• Documentation
• Chore (Related to CI or Packaging to platforms)