avoid crash in _prepare_for_brier by expanding limits if needed.

[eacharles]

Evaluation modules are failing at this line when the testing sample include any true redshifts outside the expected limits. The easiest solution is just to expand the limits to match the true redshift range. Since the binning grid is computed using a fixed size grid, this will work fine.

raise ValueError(f"Input truth values exceed the defined limits ({min(truth)}, {max(truth)}) ({limits[0]} {limits[1]})")