Explicitly scope /tc/ in az names JSON call

[mberkowski]

I should have remembered this from the beginning - the data source won't change but going forward I would like to keep an explicit /tc/ scope in all our LibGuides API integration paths. So the two new endpoints should be a little different than I gave you before.

• https://stacks.lib.umn.edu/lg/tc/az/names.json
• https://stacks.lib.umn.edu/lg/tc/subjects/names.json