Ensure http_response_header is a list<string>

[Seldaek]

Not sure if that's the proper/best use of AccessoryArrayListType, but anyway I hope the intent is clear :)

[staabm]

since no test is failling after the change it seems we are missing a NodeScopeResolverTest with a type inference assertion for this variable :)

[ondrejmirtes]

Thank you!