Some passed arguments are useless

[R-Walmsley]

Due to evolution of the functions in the epiAnalysis/useful_functions folder, some of the passed argument are useless as they are fixed further down in the plots themselves (e.g. point_specification) or are not passed to subfunctions (e.g. lower_quantile, upper_quantile).

Functions in this folder should in general be treated as documentation of what was done, rather than functions for reuse.