Simplify geom_map() examples

[thomasp85]

The examples for geom_map() takes a long time to run on cran. Seeing the deprecated state of the old mapping functionality I think we can safely reduce the examples to the bare minimum

[teunbrand]

I'm not sure if the examples actually take long to run or {sf} is just busy printing a bunch of these warnings:

hgridshift: could not find required grid(s).
pipeline: Pipeline: Bad step definition: inv (File not found or invalid)

The warnings are related to #5326.
A dirty profvis shows that for one example ~85% of time is spent in sf_transform_xy(), where these errors originate.

[teunbrand]

The hgridshift/pipeline warnings are now gone for reasons beyond my comprehension, so the geom_map() examples all run under 1 second, which I think is fine compared to some others.

Running the following:

library(ggplot2)
bench::mark(
  example("geom_map", ask = FALSE),
  example("coord_trans", ask = FALSE), # slow examples
  check = FALSE, min_iterations = 3
)

Gives:

# A tibble: 2 × 13
  expression                                   min   median `itr/sec` mem_alloc `gc/sec` n_itr  n_gc total_time result memory                  time           gc      
  <bch:expr>                              <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl> <int> <dbl>   <bch:tm> <list> <list>                  <list>         <list>  
1 "example(\"geom_map\", ask = FALSE)"     719.3ms 768.09ms     1.33     83.3MB     6.20     3    14      2.26s <NULL> <Rprofmem [11,293 × 3]> <bench_tm [3]> <tibble>
2 "example(\"coord_trans\", ask = FALSE)"    9.79s    9.82s     0.101   637.1MB     1.69     3    50     29.57s <NULL> <Rprofmem [12,313 × 3]> <bench_tm [3]> <tibble>

So geom_map() definitely doesn't have the worst runtime anymore.

Because I think the cause of the issue is magically resolved, I'll close this one.