Update High Road classifier for `minor_rail`

[nvkelso]

We're now marking rail with service tags, and we've updated the zoom and sort functions accordingly. We should consider grouping any rail with a service tag into a new minor_rail kind.

[nvkelso]

Related:

• Update High Road classifier (zoom, sort) for service and other types #332
• Railways need hierarchy #308

[nvkelso]

This would be a breaking change.