Add search term "empty" to Vacant Shop preset

[matkoniecz]

part of cleaning up Zverik/every_door#880 (I assume that it is also using iD presets)

Description, Motivation & Context

"empty" term should find disused shop to reduce confusion

Related issues

Zverik/every_door#880

Links and data

Relevant OSM Wiki links:

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Relevant tag usage stats:

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