Zemmels review: use word expression instead of formula
From Review #96:
I'm splitting hairs here, but I believe the use of the word ["formula"](https://doi-usgs.github.io/hyswap/meta/calculations.html#:\~:text=Weibull%20plotting%20position-,formula,-%2C) in the Streamflow Percentiles is incorrect. A formula expresses the relationship between quantities like "y = mx + b." I think a more appropriate term here is "expression," unless you were to set the provided expression equal to a symbol representing the plotting position like "p = \\frac{i}{n + 1}". _Changed to 'expression', thanks for your mathematical expertise!_
issue