Be less strict with deduplication of mountain peaks

[lonvia]

Follow up of: https://community.openstreetmap.org/t/openstreetmap-nominatim/6370/15

There are cases where mountain peaks with the same name are very close by and therefore have the same address. These are currently considered duplicates by Nominatim. We should be less stringent here. Possible deduplication criterions: distance, ele.