fix docs for annotate_contour

[zingale]

clim is (lower, upper), not (upper, lower)

PR Summary

in plot_modifications.py ContourCallback, we do the contours as:

levels = np.linspace(clim[0], clim[1], self.levels) 

so clim[0] is the lower limit, not upper.

PR Checklist

• [ ] New features are documented, with docstrings and narrative docs
• [ ] Adds a test for any bugs fixed. Adds tests for new features.

[zingale]

I figured it was some cosmology thing ;)