Increment feature id in tile speed layer

[datwelk]

The tile layer currently contains the same id value of "1" for all linestring features in the speeds layer. There's a comment in the codebase that says the id should be incremented for each feature, but this does not happen for the linestring features. It does happen for the turn restriction features a few lines down.

This PR addresses the issue where linestring feature ids are not incremented.