Remove examples for unexported functions.

[villegar]

Either omit these examples or export these functions.
Used ::: in documentation:

e.g.:
     man/assess_normality.Rd:
        MetaPipe:::tidy_up(c("HIST_", "ionomics_", "metapipe_"))
     man/effect_plots.Rd:
        example_data_normalised_post <-
MetaPipe:::assess_normality_postprocessing(example_data,
excluded_columns, example_data_normalised, out_prefix = out_prefix)
     man/effect_plots.Rd:
        genetic_map <- MetaPipe:::random_map(population = population,
seed = seed)
     man/effect_plots.Rd:
        MetaPipe:::tidy_up(c("EFF-", "LOD-", "metapipe"))
     man/load_raw.Rd:
        MetaPipe:::tidy_up("example_data")
     man/log_transformation.Rd:
        MetaPipe:::tidy_up("HIST")
......