briefcase variant with water droplet marker on it - for office=water_utility

[matkoniecz]

see https://pinhead.ink/#briefcase and https://pinhead.ink/#briefcase_with_bolt with similar already added entry

see https://wiki.openstreetmap.org/wiki/Tag:office%3Dwater_utility

would enable solving part of openstreetmap/id-tagging-schema#41

would be used in https://github.com/openstreetmap/id-tagging-schema/blob/main/data/presets/office/water_utility.json