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.

[rsbivand]

Please also see https://r-spatial.org/r/2023/04/10/evolution3.html, fix best by June, latest October 2023.

[rsbivand]

@lauespinosa @forchard See also https://r-spatial.org/r/2023/05/15/evolution4.html. Less than three months remain to retain this package on CRAN when rgdal which you import is withdrawn. Please replace rgdal in Imports: with sf - untried. Please act now!

[rsbivand]

@lauespinosa Less than three weeks remain to fix this.

[rsbivand]

@lauespinosa R spatial infrastructure packages maptools, rgdal and rgeos will be archived by CRAN on Monday, October 16, 2023. Your package does not pass CMD check when these packages are not available. Expect your package to be archived by CRAN October 17-18 as CRAN checks feed through and your package fails, if not updated by Monday, October 16, 2023.

No grace period is anticipated, as you have had sufficient time to update your package to remove dependencies on maptools, rgdal and/or rgeos.