Replace RColorBrewer by base R equivalent (#136)

* Replace RColorBrewer by base R equivalent

* Explicitly list grDevices as dependency

This is not strictly necessary as grDevices is a base package but it is still generally seen as better practice

DESCRIPTION

@@ -22,17 +22,17 @@ URL: https://epiverse-trace.github.io/epiCo/,
     https://github.com/epiverse-trace/epiCo
 BugReports: https://github.com/epiverse-trace/epiCo/issues
 Depends:
-    R (>= 3.2.0)
+    R (>= 4.0.0)
 Imports:
     dplyr,
     ggplot2,
     ggraph,
+    grDevices,
     igraph,
     incidence,
     leaflet,
     lubridate,
     magrittr,
-    RColorBrewer,
     rlang,
     scales,
     spdep,

R/demographics.R

@@ -819,7 +819,7 @@ occupation_plot <- function(occupation_data, sex = FALSE, q = 0.9) {
     treemapify::geom_treemap() +
     ggplot2::scale_fill_manual(
       name = "Major Group",
-      values = RColorBrewer::brewer.pal(n = 12, name = "Set3")
+      values = grDevices::palette.colors(n = 12, palette = "Set3")
     ) +
     treemapify::geom_treemap_text(
       colour = "grey16", place = "centre",
@@ -908,7 +908,7 @@ occupation_plot_circular <- function(occupation_data, q = 0.9) {
     ggraph::geom_node_circle(ggplot2::aes(fill = .data$sub_major)) +
     ggplot2::scale_fill_manual(
       name = "Major Group",
-      values = RColorBrewer::brewer.pal(n = 12, name = "Set3"),
+      values = grDevices::palette.colors(n = 12, palette = "Set3"),
       labels = circle_vertices$sub_major
     ) +
     ggraph::geom_node_text(ggplot2::aes(label = .data$unit)) +