Deprecated as_data_frame(), use as_tibble() in mr_names

[salvafern]

We shall consider to switch to as_tibble()

library(mregions)
rnames <- mr_names("MarineRegions:iho")
#> Warning: `as_data_frame()` was deprecated in tibble 2.0.0.
#> Please use `as_tibble()` instead.
#> The signature and semantics have changed, see `?as_tibble`.

^{Created on 2022-03-03 by the reprex package (v2.0.0)}