remove n_batches from daqsamplers.RateBaseCounter.sample_counts and subclasses

[gadamc]

Upon review, there's no good reason for the sample_counts method in daqsamplers.RateBaseCounter and subclasses to have a "n_batches" option. Though unlikely, if the caller needs multiple sets of samples, they can call the function multiple times. Most (all?) of the time this function is called with n_batches = 1