Log Message:
(graphics/R-ggthemes) Updated 4.2.0 to 4.2.4

# ggthemes 4.2.4
- Fixing URLs for CRAN submission again.

# ggthemes 4.2.3
- Fixing URLs for CRAN submission again.

# ggthemes 4.2.2
- Fixing URLs for CRAN submission.

# ggthemes 4.2.1
- Conditionally use the vdiffr package in tests so it complies with
  suggested package policy (#124)
- Fix error in `expect_equal` functions (#123)
- Fix errors in `geom_tufteboxplot` and `stat_fivenumber` due to
  missing imported objects from ggplot2 (#117, #121)
- Fix text labels in top axis in `theme_economist` (#115)
- Update documentation on `geom_rangeframe`; it should be used with
  `coord_cartesian(clip="off")`. (#120)