Remove point labels from water layer for lines

[rmarianski]

While working on #1135, we noticed that we are generating label points for line features. We should remove these label points from the tiles, but only for lines in the water layer.

[nvkelso]

At 11/37.6046/-122.1069, notably the creek labels are gone (and polygon labels remain, though some are appropriately culled).

After:

Before: