Remove code that gets lightcurves out of forced photometry folders directly

[jbkalmbach]

Since we don't plan on building our lightcurves using this information going forward (it was just useful to get up and running before we had NERSC databases), I think we should clear out this code and remove it from the example notebook.

If anybody thinks that's a bad idea let me know please.

[rbiswas4]

I was thinking about this and was wondering if it is worth keeping a method that will pull the forced photometry out of the repos themselves. If for some reason the database is not available, this might be a fallback option.