Fix incorrect coordinate length check for parsing polygons

[bziya]

This PR introduces a fix for a bug that I found when parsing data from Melbourne Australia. For some reason there is a building in the downloaded data that I guess did not have the correct data to parse properly.

I followed the stack trace below:

error: Each LinearRing of a Polygon must have 4 or more Positions.
at polygon (C:\Users\xxx\Documents\subwaybuilder-patcher\node_modules@turf\helpers\dist\esm\index.js:97:17)
at <anonymous> (C:\Users\xxx\Documents\subwaybuilder-patcher\scripts\process_data.js:288:34)
at forEach (1:11)
at processBuildings (C:\Users\xxx\Documents\subwaybuilder-patcher\scripts\process_data.js:265:16)
at <anonymous> (C:\Users\xxx\Documents\subwaybuilder-patcher\scripts\process_data.js:435:30)

I saw that in the code it is checking that the polygon has at least 3 positions, when the code in the turf module will throw an error if there are <4 positions.

I have modified the code to run a check before the turf.polygon() function is called that there are enough positions, otherwise the building in skipped.