`GeomMap$draw_panel()` does not use `ggname()` to edit prefix when returning its `polygonGrob()`

[trevorld]

• Most Geom's draw_panel() methods use ggname() to edit the name of the returned grob but for some reason GeomMap does not:

  ggplot2/R/geom-map.R

  Line 145 in 28ec18f

  polygonGrob(coords$x, coords$y, default.units = "native", id = grob_id,

• I wasn't sure if this is deliberate or an oversight but when I briefly searched I couldn't see a discussion for why this Geom should be an exception.