fix(app-builder-lib): Overriding OutgoingHttpHeaders schema props

[mmaietta]

fix: Overriding additionalProperties to allow electron-builder's schema validator to read requestHeaders. It seems that the schema generator does not read NodeJS.Dict<number | string | string[]> properly, which then doesn't allow any entries for publish.requestHeaders to be provided.
Fixes: #6635

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🦋 Changeset detected

Latest commit: b3e0252

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 8 packages

Name	Type
app-builder-lib	Patch
dmg-builder	Patch
electron-builder-squirrel-windows	Patch
electron-builder	Patch
electron-forge-maker-appimage	Patch
electron-forge-maker-nsis-web	Patch
electron-forge-maker-nsis	Patch
electron-forge-maker-snap	Patch

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