n_target should be n_targets

[londumas]

redrock/py/redrock/external/boss.py

Line 314 in d0a3260

n_target = args.ntargets

In the new master, rrboss is broken: n_target should be n_targets.
Why even creating n_targets? We could simply use args.ntargets

    n_targets = None
    if args.ntargets is not None:
        n_targets = args.ntargets

    first_target = None
    if args.mintarget is not None:
        first_target = args.mintarget
    elif n_targets is not None:
        first_target = 0

        if args.ntargets is not None:
            targets = targets[first_target:first_target+n_targets]
            meta = meta[first_target:first_target+n_targets]

[sbailey]

Thanks for catching this (unfortunately I only tested rrdesi, not rrboss). Please go ahead and fix (but make sure that all combinations work: only --mintarget, only --ntargets, or both --mintarget and --ntargets).

Related to #70 #71 and #73.