Name rendered twice on power/building

[jengelh]

Observed:
The name of building (way 737365087) is rendered twice.
https://osm.org/#map=19/51.54569/9.76438

Expected: just one label should be enough.

[jeisenbe]

This building is also tagged as a power=generator which gets text-dy: 10, so the building name is being displayed at the center, and the power generator name (which is the same) is displayed just below.

The text-dy is necessary for wind generators, which are displayed with an icon, but should not be used for other types of generators.

I caused this bug in #3515, sorry.