geojson_file in urban_geometry_creation doesn't use workflow.runner.findFile

[DavidGoldwasser]

When a measure requires a file, starting in OpenStudio 2.0 we have the ability to just use a file name as the argument, and rely on the "file_paths" described in the OSW.

This is used on ChangeBuildingLocation, shown below.
https://github.com/NREL/openstudio-common-measures-gem/blob/develop/lib/measures/ChangeBuildingLocation/measure.rb#L138-L145

This allows you to enter the file name only, a relative path, or a full path. This is very helpful in making OSW's transportable without having to alter arguments.