`ggplot2::ggpar()` has a namespace conflict with `ggpubr::ggpar()`

[teunbrand]

In #5867, we introduced ggpar() to ggplot2. It helps translating ggplot2 settings, which are often in mm (historical errors aside) to {grid} settings.

ggpubr::ggpar() does something else entirely. From my reading of it, it controls parts of the theme, guides and orientation of plots.

The namespace conflict is a source of several reverse dependency failures.