Remove use of rgdal

[rsbivand]

This package has strong dependence on at least one of rgdal, rgeos or maptools, but does not seem to use any functionality in code. The usage may have been in raster, which now uses terra instead, or may be in examples or vignettes. Please move all use of rgdal, rgeos or maptools to Suggests: and protect any use against these packages not being present. The packages will be archived in October 2023. See https://r-spatial.org/r/2022/12/14/evolution2.html and https://rsbivand.github.io/csds_jan23/bivand_csds_ssg_230117.pdf and perhaps view https://www.youtube.com/watch?v=TlpjIqTPMCA&list=PLzREt6r1NenmWEidssmLm-VO_YmAh4pq9&index=1.