Fix office results containing alternates

[digitalaun]

I encountered an issue getting office results for code 2248524. The problem was unlike postaldata.json, alternates in officedata.json were missing the alternates field. This resulted in the following error when instantiating OfficeCodeBase for each alternate:

TypeError("() missing 1 required positional argument: 'alternates'")

My original approach was to modify the results at run time, but in the end I went with modifying prep.py to always include alternates and updated the office data. Let me know if you prefer another approach.

Also renamed a test that was shadowing another one with the same name.

[polm]

Thanks for catching that, that looks fine to me.